Silkworm rearing technology

Intermediate
Vocational Course
Second Year
SILKWORMING REARING
TECHNOLOGY
for the Course of Sericulture
State Institute of Vocational Education
Directorate of Intermediate Education
Govt. of Andhra Pradesh, Hyderabad.

AUTHORS
E. Rama Devi, B.Sc., P.G.D.S.,
P.T. Junior Lecturer in Sericulture,
Govt. Pingle Junior College (Girls),
Waddepally, Hanamkonda - 506 370.
T. Karuna, M.Sc., P.G.D.S.,
P.T. Junior Lecturer in Sericulture,
Govt. Junior College,
Shadnagar, Rangareddy Dist.
EDITOR
Dr. Ponna Srinivas
M.Sc., B.Ed., Ph.D., PGDCMP., CYP-PGDYDW,
Associate Professor in Zoology,
Pingle Govt. College for Women,
Waddepally, Hanamkonda, Warangal Dist.

1. Hatching and Brushing 01
2. Chawki Rearing 11
3. Late age Rearing 41
4. Effective Rate of Rearing (ERR) 57
5. Spinning and Mounting 65
6. Silkworm Diseases 81
7. Silkworm Pests 114
8. Economis 126
Reference Books 138
Glossary 140
CONTENTS

1.1. INTRODUCTION
Silkworm eggs are of two types i.e. hibernating and non-hibernating
eggs. Further processing of the eggs depends upon whether they are of the
diapausing or the non-diapausing type. Univoltine races lay only diapausing
eggs. Multivoltine races lay only non-hibernating eggs while the behaviour
of the eggs of the bivoltine is intermediate. Except multivoltine, uni and
bivoltine race eggs are hibernating eggs which require special treatment to
make them hatch. These eggs are stored till the next season or awakened
from diapause artificially. The eggs stored are taken out and subjected to
incubation to achieve uniform hatching on a desired day.This can be achieved
by exposing the eggs to certain range of environmental conditions. The in-
cubation of egge is one of the essential parameter in silkworm rearing.
Silkworm rearing requires care and skill. Since various rearing op-
erations are important which finally reflect on cocoon quality and quantity.
The rearing room activity starts with brushing of newly hatched silkworms.
Since silkworms are susceptible for any kind of diseases and cannot with-
stand to any changes in the environmental conditions, the rearing room should
be prepared in such a way not to hamper the growth of the worms. On the
other hand mulberry garden should posses 5-6 leaves. It is better to tap the
shoots 25-30 days prior to the date of brushing.
The equipments such as foam rubber strips, chawk rearing trays,
feather (white), paraffin paper, chopping board and knife, mats are kept ready for
rearing.
The desire race of silkworm DFLs (Diseased Free Layings) are pro-
cured from grainage. The eggs are protected from ants, rats. They are incu-
bated well and later kept in black box. The process of brushing and methods
are explained in this chapter.
1.2. HATCHING
Eggs after reaching blue egg stage are kept in black box/paper/cloth
and kept in dark. In this way early maturing embryos are prevented from
hatching and late maturing embryos are given time to develop and catch up
with the early maturing ones. Thus all the eggs reach to blue egg stage. The
eggs hatch out in
1
HATCHING AND BRUSHING

2 SILKWORM REARING TECHNOLOGY
responce to phototropic stimulus.
This mehod favours hatching more
than 90 percent. If hatching is not uni-
form and only 50-60 percent of eggs
hatch on the first day, brushing can
be postphoned to next day as well. If
necessary hatched worms can be
separated and kept in tissue paper and
stored in fridge at 100
C.When the sec-
ond batch hatch our the refrigrated
eggs are mixed and brushed together.
Even blue egg stages can also be pre-
served at 50C for 2-3 days.
Silkworm eggs are available loosely and on egg cards. The newly
developed larvae breaks out the egg shell and comes out, and is called hatch-
ing. The hatched larvae are collected and reared. The newly hatched larvae
are black, hairy and look like small ants and are called “ants” or “kego”
(Fig. 1.1). Is is always better to brush the larvae in the morning. Th eggs
exposed in early hours or hot hours results in irregular hatching. Generally
brushing should not be delayed. If necessary, can be postphoned to next day
whne hatching is irregular. Brushing should be completed in the morning/
cool hours of the day. Freshly emerged larvae can also be preserved at 7-
100
C for one day.
Fig. 1.1 Bombix Embryonic Stages
Fig. 1.2. Hatching

HATCHING AND BRUSHING 3
x 100
Hatching percentage =
Total No. of eggs hatched
Total No. of eggs
x 100
Unfertilised egg percentage =
Total no. of eggs = Good eggs + dead eggs.
MODEL PROBLEM :
In a laying, total eggs are 445, our of which 415 hatched. Findout
hatching and dead eggs percentage.
Total eggs = 445
Hatched = 415
Unfertilised eggs = Total eggs - hatched eggs
= 445 - 415
= 30
Dead/unfertilised eggs = 30
Hatching percentage = x 100 = 93.25%
Unfertilised egg percentage = x 100 = 6.74%
Total No. of dead / unfertilised eggs
Total No. of eggs
415
445
30
445
1.3. HATCHING PERCENTAGE
The ratio between hatched eggs and total eggs in a laying is called
“hatching percentage”. The hatched eggs, unfertilized or dead egg number
is counted individually for calculating the percentage. This can be done
using a colour ink pen and later it is calculated using the following formu-
lae and method.

= 475 - 20
= 455
Hatching percentage = x 100 = 95.78 %
Dead egg percentage = x 100 = 4.21 %
EXAMPLE - 2
In a rearing centre 2620 eggs hatched and 70 eggs did not. Find out
hatching and dead eggs percentage.
Hatched eggs = 2620
Dead eggs = 70
Total eggs = hatched eggs + dead eggs
= 2620 + 70
= 2690
Hatching percentage = x 100 = 97.39 %
Dead egg percentage = x 100 = 2.6%
445
475
20
475
2620
2690
70
2690
EXAMPLE - 1 :
In a laying total eggs are 475 out of which 20 eggs did not hatch.
Findout hatching and dead eggs percentage.
Total eggs = 475
Dead eggs = 20
Good eggs = Total eggs - dead eggs

1.4. BRUSHING
When the eggs hatch, the emerged larvae are to be collected for rear-
ing. This process of separating kego/ants from egg shell is called “brush-
ing”. It means placing of mulberry leaves on a frame to attract the larvae so
that they will be separated from their shells. The optimum time for brushing
is around 10am when the humidity is 85-90% and temperature 270
C.
Normally hatching starts at 5-6 am when the eggs are exposed to
early sun rays. Uniform hatching can be expected by 7-8 am. After 2 hours
the newly hatching worms develop appetite and begin to crawl. Thus the
suitable time for brushing would be 10am but once again it depends upon
the weather conditions.
Before brushing, rearing facilities should be prepared according to
the number of silkworms to be reared. Tender mulberry leaves should be
chopped to 3-5 mm size. When the worms crawl over into the tray worm
bodies should be disinfected for disease prevention by using a fine-mesh
sieve to dust a fine powder of formalin (3%).
It is of two types i.e. brushing of loose eggs and brushing from egg cards.
Fig. 1.3. Incubation Process

1.4.1. BRUSHING OF LOOSE EGGS
The eggs are spread evenly in one layer in the box and kept in black
box at blue egg stage. On the next day when all eggs reach blue egg stage
they are removed from black box and covered with a thin perforated cloth or
a fine-mesh or finely perforated and this paper (Fig.1.3).
This covering is placed in such a way that it just touched the upper
surface of the eggs. Then just before brushing, chopped mulberry leaves are
sprinkled on the top of the net or cloth or paper. This mulberry leaf attracts
the hatched worms to crawl on to the upper surface. When maximum num-
ber of worms hatch out and crawl on to the paper they are collected in to
rearing tray.
Fig. 1.4. Brushing of Loose Eggs

1.4.2 BRUSHING FROM EGG CARDS
a. Tapping method :
The hatched larvae which crawl towards the edges or corners of the
egg sheet are collected into rearing tray using a feather. The egg
sheet is hold upside down just above the rearing seat and tapped
from above. The larvae drop on to the rearing seat. Then the dropped
larvae are brushed together with feather and fed for the first time.
b. Feather method :
The hatched larvae which crawl towards the edge or corners of the
sheet are collected gently with a feather. Hold the egg sheet slant
wise to the rearing seat and brush off the larvae from the egg sheet to
the rearing seat with the help of a feather (Fig. 1.4). Later worms are
fed with finely chopped mulberry leaf.
c. Brushing with mulberry leaves :
Mulberry leaves chopped to 0.5Sq. cm size are sprinkled on the egg
sheets when larvae hatch out. The mulberry leaf attracts the larvae.
After 10 minutes the egg sheet is turned upside down and larvae
along with mulberry leaf are transferred to rearing tray using feather.
d. Husk – feeding method :
Finely powdered paddy husk is sprinkled thinly, evenly on the egg
sheet when the larvae hatch. The larvae crawl over the layer of paddy
husk. Then finely chopped mulberry leaves are sprinkled on the
worms and finally transferred to rearing tray using feather.
Fig. 1.5. Brushing by Feather

Fig. 1.6. Newly Hatched Larvae
Fig. 1.7. Disinfection Newly
Hatched Larvae
Fig. 1.8. Feeding of
Hatched Larvae

SUMMARY
Incubation of silkworms eggs favour maximum hatching.
Incubation room, chamber must be clean and should possess required
chemicals, disinfectants, equipments.
Non-hibernating eggs and after acid treatment requires 80-85% hu-
midity and 24-250
C temperature right from the beginning.
Cold stored eggs are gradually brought to normal room temperature.
Temperature, humidity, light are equally important during
incumbation of eggs.
Eggs are kept under a photoperiod of 16 hours daily until 30-40% of
the eggs reach blue egg stage.
Blue egg stage eggs are kept in dark/black boxes for more uniform
hatching on the next day.
Hatching can be delayed at blue egg stage by cold storing for about a
week at 90
C.
Incubated eggs are handled properly for good hatching percentage.
The eggs before (48) hours hatching reach head pigmentation or pin
head stage and are called eye spot stage. On the following day em-
bryo turns black and called blue egg stage.
Blue egg stage are kept in black boxes for maximum hatching per-
centage.
Blue egg stage eggs can be preserved at 50
C for 2-3 days.
Newly developed larva breaks the egg shell and comes out, the
process is called hatching.
Newly hatched larva is called and or kego.
The larvae are to be brushed in cool hours of the day,
Calculation of hatching percentage is carried after brushing.
Prior to brushing the rearing room and required equipment is kept
ready.
Brushing is important and first activity in rearing.
It is a process/activity ensures to separate newly hatched worms from
the egg shells.
This activity starts in the early hours of the day and decreases as the
daylight increases.

The required humidity and temperature favours brushing.
Brushing is done in two methods i.e. loose egg brushing, brushing
from egg cards.
While brushing loose eggs, finely perforated, thin paper is spread
and later finely chopped mulberry leaf is sprinkled. Crawled worms
are collected.
Brushing from egg cards has different methods.Among them feather
method is popular.
While brushing care must be taken not to damage the silk worms.
QUESTIONS
I. SHORT QUESTIONS
1. Define blue egg stage
2. Define black boxing
3. Define ‘kego’or ‘ant’
4. Mention incubation temperature and humidity.
5. What is handling of eggs ?
6. What is eye spot stage ?
7. Mention principle for calculating hatching percentage.
8. Define Brushing
9. What is the best time for brushing ?
10. Mention required temperature and humidity for brushing.
11. Mention brushing equipments.
12. What is the popular method of brushing ?
13. List out methods of brushing ?
14. Define D.F.L.
II. ESSAY QUESTIONS
1. Write about black boxing of silkworm eggs. ?
2.. Write short notes on
a) Hatching b) Blue egg stgage
3. Calculate hatching percentage using these values
Total eggs = 530, Hatched eggs = 512.
4. Detail the process of brushing of loose eggs.
5. Describe methods of brushing from egg card.

2.1. INTRODUCTION
The life cycle of silkworm consists of egg, larva, pupa (cocoon) and
adultstages. Among these four stages, larval stage is the only feeding and
activestage. Thedurationoflarvalperiodformhatchingtospinningisabout
26 days. During this long duration the larvae grow in size and enter cocoon
(pupal)stage. To accommodatate the larval body growth the larvae undergo
fourmoultsandtherebyhecompletelarvaldurationcanbeclearlydifferen-
tiatedintofiveinstarsorstadia. Thefirstthreeinstars(tillthethirdmoult)
are known as young age or chawki and the last two instars are called as late
age worms.
2.2 IMPORTANCE OF CHAWKI REARING
Youngageorchawkirearingandlateagerearingtechniquesare dif-
ferent.Bothnutritionalandecologicalrequirementsduringthesetwostages
are different. The essential point in rearing of young silkworms is to get
strong and sturdy silkworms. The success of sericulture depends to a large
extent on the successful rearing of young worms. Young age worms are
more resistance to high temperature and humidity and grow healthier,
ensuring success of cocoon crop. The first character of young silkworms is
that, they grow extremely fast. To support their fast growth, they must be
given highly nutritious sufficient mulberry leaves. Undergrown mulberry
makes silkworms susceptible to disease growth becomes uneven, reflects
on rearing resulting in poor cocoon crop.
Therefore young silkworms are fed with tender and succulent
mulberry leaves. The leaf eating time is shorter in earlier stages then later
instars. However the total leaf requirement of silkworm larva in only 6.33
percent,duringchawkirearinguptoIIImoult.Butbodyweightincreasesby
400 times, while 300 times increase in body size and 500 times increases in
silk gland weight are achieved during young stage provided the conditions
andmethodsofrearingareideal.Furthertherateofincreaseinbodyweight
of larva per given time is more in the first instar and it decreases with the
age. Theeffectsifinsecticidesdisinfectants,injuriousgasesetc,onthe larvae
are more in the earlier instars than in the later instars. Keeping in view of
above points the young worm rearing must be carried out with maximum care.
2
CHAWKI REARING

2.3. ENVIROMENTAL CONDITIONS
Since silkworms have been domesticated for many centuries, they
are by nature quite delicate and are very sensitive to environmental condi-
tions. The ecological factors chiefly temperature, humidity, light and air
during rearing have a significant in influence on the growth of larva and
ultimately on cocoon crop quality. Of course the other factors like quality
and quantity of leaf supply and techniques of rearing adopted such as feed-
ing,cleaning,spacingetc,arealsotobeconsidered. The influence of envi-
ronmental conditions is not the same throughout the rearing period, but var-
iesindifferent stages of larval growth depending upon the physiological
condition and voltinism of the silkworm.
2.3.1. TEMPERATURE :
Temperature plays a vital role on the growth of the silkworms. As
silkworms are cold blooded animals, temperature will have a direct effect
on various physiological activities. Rise in temperature increases various
functions and with a fall the activities are decreases. Increased temperature
accelerates larval growth and shortens the larval period. On the other hand
at low temperature the growth is slow and larval period is prolonged. The
optimum temperature for normal growth of silkworms is between 200
C and
280
C and the desirable temperature for maximum productivity ranges from
230
Cto280
C. temperature above 300
Cdirectlyaffectsthehealthoftheworm.
Ifthetemperatureisbelow200
Callthephysiologicalactivitiesareretarded,
especially in early instars, as a result worms become too weak and suscep-
tible to diseases. The temperature requirements during the early instars
(I,II,III)ishighandthewormsfeedactivelyandgrowveryvigorously.Such
vigorousworms,canstandbetterevenatadverseconditionsinlaterinstars.
Optimum rearing temperature for rearing is 240
–280
C.Ingeneraltheearly
instarlarvaeareresistanttohightemperatureanditalsohelpsinimproving
survival rate and cocoon characters.
The temperature has a direct correlation with the growth of silk-
worms and wide fluctuation of temperature is harmful and as for as possible
it should be avoided. The optimum temperature required for rearing silk-
worms of differentearlyinstarsareasfollows.
I 260
C - 280
C
II 260
C - 280
C
III 240
C - 260
C
Stageof W orms Optimum Temperature

CHAWKI REARING 13
2.3.1.1. Regulation of Temperature
Generally the room temperature is low during winter and rainy day
which should be regulated by heating with electric heaters or charcoal fires.
Electrical heaters are best since they do not emit any injurious gases. When
electricityiscostlyandnotavailable,properlydriedcharcoalandcanbeused.
Inthiscasehoweverthelivecindersshouldbecoveredwithalayerofashfor
more regulated room to raise the temperature should be avoided. Because the
carbondioxide and other gases emitted in this process are injurious to silk-
worms. Besides the above processes the doors and windows should be kept
closed. During nights to keep out the cold. Late in the day, as the outside
temperature goes up doors and windows should be opened to allow warm air
in to the room. In Andhra Pradesh, Karnataka and W est Bengal except for a
few days of winter and rainy days, the temperature is often above the opti-
mum level. Thus it is problem for the rearer to lower the temperature rather
than heating up of rearing room. This sort of temperature is adverse to silk-
worms. This adverse effects to a certain extent be mitigated through proper
designing of the rearing house and by ensuring adequate ventilation and free
circulationofair.
During summer season when the day temperature is high, all the win-
dows should be kept open during night, to bring down the temperature. And
early in the morning all the windows and doors should be opened so that the
cool air from outside is allowed into the rearing room to bring down the tem-
perature. When the sun rises and the temperature goes up, doors and windows
should be closed. Besides this windows and doors are covered by wet gunny
clothonahotdaytoreducethetemperature.Otherwiseaircoolerscanalsobe
used for this purpose.
2.3.2. Humidity
Itplaysavitalroleinsilkwormrearing. The combined effectofboth
temperature and humidity largely determines the satisfactory growth of the
silkworms and production of good quality cocoons. Its role is both direct and
indirect. It directly influences the physiological functions of the silkworm.
The young age silkworms can withstand to high humidity conditions better
than later age worms and under such condition the growth is vigorous. The
humidity conditions for different early age worms are as follows.
I 85
II 85
III 80
Age Relative Humidity %

Humidity indirectly influences the rate of withering of the leaves in
the silkworms beds. Under dry conditions the leaves wither very fast and
become unsuitable for feeding. This effects growth of the larvae and also
results in wastage of leaf fed. Retorded growth of young larvae makes them
weak and susceptible to disease. At a humidity of 90 percent or higher,if
temperature is kept at 260
– 280
C, they can grow without being greatly
affected. Therefore the humidity is kept high to prevent mulberry leaf
withering.
2.3.2.1. Regulation of humidity
Liketemperature,humidityalsofluctuateswidelynotonlyfromsea-
sontoseasonbutalsowithinthedayitselfduringanyseason. Thereforeitis
amustfortherearertoregulateit.Forthispurposeparaffinpaperisusedfor
rearing beds during chawki rearing to raise humidity. Other wise wet foam
rubber pads or paper pads soaked in water can also be used to increase hu-
midity in the beds. However it is important to lower humidity to 70 per cent
or below during the moulting in each instar to facilities uniform and good
moulting. Otherwise it results in
a. silkworms remain under the net
b. uneven growth
c. become susceptible to disease
d. bed cleaning requires much labour
e. missing worm number increases
Therefore rearer must remember the drying and disinfection of bed
during moulting without fail. Removal of paraffin paper during moulting
raisesthedryingeffect.
2.3.3. Air
Like other animals silkworms also require fresh air. By respiration
of silkworms carbon dioxide gas is released in the rearing bed. Besides this
carbon monoxide, ammonia, sulphur dioxide etc., are also released in the
rearing room by burning of charcoal to raise temperature. These gases are
injurious to silkworms. Therefore care should be taken to allow fresh air
through proper ventilation to keep the toxic gases at a low level. If CO2
exceeds to 2 per cent concentration, the growth of silkworm is retarded.
Insecticides and disinfectants are also avoided in the rearing room.

CHAWKI REARING 15
Air plays an important role in regulating room temperature and hu-
midity.Artificial air circulation is useful for bringing down high tempera-
ture and humidity.
2.3.4. Light
Silkworms are photosensitive. They have a tendency to crawl
towards dim light. They do not like either strong light or complete dark-
ness. The larval moult is uniform when silkworms are reared in 16 hours
light and 8 hours darkness.
2.4. QUALITY OF MULBERRY LEAF
The Mulberry leaf is the exclusive food of the silkworms (Bombyx
mori). The growth of the silkworm very much depends on the quality of
leavesfedtothem. Theleafqualityisinfluencedbyvariousfactorssuchas
soil,pruning,fertilizer, rainfall, irrigation etc. with these conditions mul-
berry grows luxuriously with rich contents of proteins and carbohydrates.
Furthertheleavesarealsosucculentduetohighnutrientcontent. Thistype
of leaves are edible for silkworms for better growth and to produce good
cocoons. Leaves of mulberry grown on loamy soil contain more water,pro-
tein and less carbohydrate and fibre. Further the leaves mature slowly.
Mulberry leaves form trees grown in sandy or gravel soil mature quickly
becoming rough and coarse. These leaves contain less moisture, protein
and more carbohydrates and fibre. Application of balanced fertilizers with
major elements required by the plants improves both physical and chemical
properties of the leaves. In well distributed rainfall or irrigated conditions
themulberrygrowthisvigorous.Leavesoftheseplantsarerichinnutritive
value and are soft and succulent.
In areas where temperature fluctuations during night and day are
hightheleafqualitybecomessuperior.Thenutrientssynthesizedduringthe
day are least utilized during the cool night hours. Therefore the nutrients
arebetterpreservedintheleaves.
Mulberryraisedunderidealagronomicconditionsarebetterforrear-
ing silkworms. The conditions are as follows.
1. Good soil, neither two clayey nor too sandy,butnotacidic.
2. Application of optimum and balanced fertilizers
3. Suitable cultural operations
4. Assuredirrigationsorrainfall.

On the above said conditions the leaves are rich in protein, and
carbohydrates besides high leaf moisture. The leaves are soft and succu-
lent. This type of leaves are easily digested and best utilized.
From the quality point of view the requirements of young worms
are completely different from those of late age worms. The chawki worms
require tender, soft and succulent leaf having higher contents of moisture,
protein, sugars and less starch and fibre. However too soft leaves are not
suitable for the worms.
Thequalityofleafmayvaryconsiderablyfromseasontoseason.In
summer the leaves grow and mature fast, but wither quickly.Itslifeinthe
rearing bed becomes short favouring to increase number of feeds per day.
In rainy season, the leaves grow and mature fast and contain more mois-
ture.Hencethelifeislongerthereforereducesthenumberoffeedsperday.
Because of high moisture content, humidity of the beds increases. There-
fore it is necessary to keep down the humidity of the bed under control
throughfeedingofreducedquantityofleafandmorenatureleafcontaining
less moisture. This can be achieved when leaves required for second age
are fed to first instar larvae and the normal third age leaves to the second
instar larvae and so on. In cold season the mulberry growth is slower and
leaves mature gradually.These leaves have better quality, optimum mois-
ture and better feed value. This type of leaves neither wither nor increase
bed humidity leading to successful crops. Morning time is the proper time
forpickingthemulberryleaves,planningthetotalleafrequirementsofthe
day.
2.5. Leaf Selection
Mulberry for young silkworms has a great effect on the growth and
healthofsilkworm. Therefore selection of leaves should be done carefully.
The leaves for your silkworms must be soft, tender,richinwatercontent,
protein,carbohydratesetc.. Thereishighcorrelationbetweenmoisturecon-
tent in the top tender leaves and chawki worm growth and moulting. There-
foreforpluckingthecorrectleavesforyoungworms,thelargestglossyleaf
method is adopted.
2.5.1. Glossy leaf method
For the identification of glossy leaf, hold the upper part of shootr
lightly, and move the hand upward gently.Then appears a large leaf which
standsoutatthetop(Fig.2.1.a.b.).thisisidentifiedaslargestglossyleaf.

CHAWKI REARING 17
otherwiseholdingtheupperpartoftheshooterlightlybetweenfingers,and
bendithorizontally.Thenaleadstandsuprightisidentifiedaslargestglossy
leaf(Fig.2.1c).
Now the first instar are fed with 4th and 5th leaves downward from
thebaseofglossyleaf,forseconinstar5th-7thleaves,forthirdinstar7-8
leaves to downward are plucked.
Fig. 2.1 Glossy Leaf Selection (A,B,C)

Fig. 2.2 Lenticel and Bud Method

CHAWKI REARING 19
2.5.2. Lenticel and Bud (LB) Method
Inthismethodthecolourofthelenticelandauxiliarybudsareused
to harvest good leaves corresponding to the stage go worms. The colour of
auxiliarybudschangesfromthetoptothebottomofthebranch. The colours
from top to bottom are green, apical brownish, striped, non-accomplished
and accomplished buds (Fig. 2.2)
Leaf with yellowish lenticel at the base of leaf petiole found above
theapicalbrownishbudareusedforfirstinstar. Leaves from the brownish
lenticel through the apical brownish bud are for second instar.The leaves
from the brownish lenticel through the non-accomplished bud are used for
thirdinstar.
2.5.2.1. Leaf Preservation
It is important not only to produce highly nutritious and succulent
leave but also to preserve them after harvest till they are consumed by the
worm. The freshly harvested succulent leaves undergo nutrient changes
following harvest. In not day the loss of moisture affects the edibility or
palatabilityoftheleavesforsilkworms.Forthisrelativehumidityismain-
tained in the rearing room to prevent withering of the leaves. Silkworms do
not feed on withered leaves. The consumption of the worms changes in
accordance with the moisture content the leaves. When large quantity of
leafisrequiredforrearingitrequiresmushtimeforleafharvest. Thus har-
vested leaf may dry quickly if not collected in proper baskets covered with
wet gunny cloths or put in leaf chamber. During leaf storage high humidity
and low temperature are maintained in the preservation room and periodic
turning of leaves is suggested to avoid fermentation and to release the
repiratory heat. In this conditions, leaves absorb more moisture and remain
freshforalongertimeintherearingbeds.Generallypreservedleavesshow
higher moisture content and protein. This high moisture content helps di-
gestibility of worms. Large quantity of leaf can be stored on a clean floor,
overgunnyclothinlooselayerswithadequateairpocketsandcoveredwith
wet gunny cloth. In summer sprinkling of water on the leaves and frequent
wetting of gunny cloth covered are required (Fig. 2.3.a,b,c).
Ingeneralmulberryleavesshouldbepreservedinamoistandclean
place. The tender leaves meant for young worms can be preserved in boxes,
baskets or jars covered with clean wet cloths. In India leaves for young
worms are preserved in eartherned pots covered with wet cloths and places
in moist sand.

Preservation of leaves as fresh as possible helps to reduce the num-
ber of feeds, there by cuts down the labour cost involved in rearing.
Fig. 2.3. Leaf Preservation

CHAWKI REARING 21
2.6. FEEDING SCHEDULES
2.6.1. Feeding
Silkworms are fed to satisfy their appetites. Thereby uniform and
health growth of silkworms can be achieved. For this, quality leaves are to
be preserved and rearing beds are kept clean. Feeding with too many leaves
in not economics. The main objectives of feeding are;
1. tosatisfyheappetiteoflarvae
2. to promote eating and digestion of leaves by larvae
3. to keep the quality of leaves during eating
4. to keep rearing beds clean
5. to avoid wastage of leaves and labour.
Generallyearlyagesilkwormseatleavesthesurface. Whilelateage
worms form the edges. The feeding activity of each instar of silkworm can
be conveniently into seven stages.
1. Firstfeedingstage
2. Sparse eating stage
3. Moderate eating stage
4. Actively eating stage
5. Premoulating stage
6. Last feeding stage
7. Moulting stage
Fig. 2.4. Chawki Worms
Fig. 2.5. Feeding

Atthebeginningofeachstagethewormshaveagreatappetite. The
larvaehavegoodappetiteatthefirstfeedingstage,andcomparativelylittle
appetite at the sparse eating and moderate eating stages. They eat much at
theactiveeatingstage. Afterwardsappetiteincreasestilllastfeedingstage
after which eats nothing and enters moulting stage. Thisappetitefallsvery
rapidlyintheearlypartoftheageandthengraduallyincreasestotheendof
the age as the worm reach moulting time. If the worms are active in their
movements, their appetite is keen and requires more food. On the other
hand of the worms are dull feeding is not required.
When the worms are of a rusty colour, having come out of moult
willbeveryhungry.Astherustcolourdecreasestheappetitedeclines.Later
abluetintappearsatthesegmentswhichgraduallyspreadsovertheworms.
Thisbluetingeisanindicationofreturningtoappetitewhichgrowssteadily.
When appetite reaches its maximum, whitish body colour mixes with the
blue. Then worm turns to light amber colour and prepares to moult appetite
falls.
Themainideaoffeedingistonourishallthewormssimultaneously
and equally to ensure uniform growth. In this process the worms are given
enough time to eat and also prevent wastage of leaves in any way,toin-
creasetheirbodyweightandsizeineachage. Theweightofleavesrequired
forfoodduringeachageis2½ timestheirincreaseinweightfromthefirst
to the growth age. In the fifth stage the leaf consumption is 4 ½ times of
their developments in body.The increase in the weight of worms during the
rearing varies with season and race.
2.6.2. Growth of worms
Silkworms show high rate of growth. The growth by weight, be-
tween hatching and final spinning of cocoons stage is 10,000 times which
is achieved in a matter of 24 to 25 days. For achieving full growth of silk-
worm new techniques of rearing are following by which worm grows to a
weight of 4-5 gms. These worms are healthy and produce cocoons of 1.75-
2.0gr.andaboveinweight. The growth of the worms mainly depends upon
the amount of mulberry ingested and digested (Table2.1,2.2). The growth
rate of silkworm varies with meteorogical conditions. When the tempera-
ture is high the silkworms grows fast, but low temperature slows down the
growthrate. The weight of worms increases 15 times from hatching to the
endof1age,4-5timesatIIage,5timesatIIIage;5timesatIVageand5
timesat V age(Table2.3)
Thus the weight of full grown larvae will be fromn 8,000 – 10,000
times that of newly hatched larvae which is about 0.0003 to 0.0005 gm
(Table 2.2). the quantity of leaf required of rearing 50 layings or a box of
20,000eggs,uptoIIIinstararegivenin Table2.4.

CHAWKI REARING 23
Table 2.1 Ingestion and Percentage of Digestion
Source: Synthetic Sericulture
Table 2.2 Amount of mulberry ingested and digester by silkworms.
(per 1000 larvae in green weight)
%ofTotal
amountDigested
Amountof
leavessupplied(gr)
%ofIngestion
Amountof
LeavesIngested(gr)
Stage
%ofDigestion
AmountofLeaves
digested(gr)
%oftheTotalAmount
ingested(gr)
I
II
III
IV
V
59.8
223.4
970.0
5,333.0
35,150.0
14.4
88.8
480.4
2,419.7
19,610.5
24.4
39.7
49.5
45.4
55.7
0.06
0.37
1.86
10.16
87.55
7.7
45.3
192.3
961.2
7,655.1
53.4
51.0
40.0
39.7
39.1
0.08
0.48
1.90
10.30
87.24
Total41,736.2 22,163.8 54.2 100.00 8,861.6 39.2 100.00

Table 2.3. Silkworms body weight and size, during differentinstars.
When weighed
Increasein
weight (No.of times)
Increaseinsize
(size of newly brushed worms)
Immediately after hatching
2nd instar after moult
3rdinstaraftermoult
4thinstaraftermoult
5thinstaraftermoult
At the height of growth
1
10-15
75-100
350-500
1,800-2,200
8,000-10,000
--
10-12 times
50-80 times
300-400 times
1500-1800 times
8800-9000 times
Table 2.5. Care for nearing of silkworms during rainy season
WORM
HEALTH
FEEDING TIME
Reduces feeding
leaves but increase
feeding time
QUALITY OF FOOD
W atercontentinthe
leaves should not be
too high
AERATION
Ventilation, more
bed cleaning
CLIMATIC
CONDITIONS
Temperature Humidity
More liming and body
disinfection with
chlorine solution

Table 2.4 Leaf Requirements
Fig. 2.6. Leaf Chopping
2.6.3. Preparation of leaves for feeding young worms.
Depending on the size of the worms complete leaves can’tbeused
for chawki worms. Further leaf quality can also be influenced by the pro-
cess of chopping. However the cut surfaces of leaf leads to loss of mois-
ture. Thereforeitisessentialtoadjustthechoppingofleafsoastoprotect
thequalityofleaf. The withering of leaf in rearing bed can be prevented
using paraffin paper and foam rubber or paper soaked in water.This in-
duces to raise humidity In the rearing beds.
Quantity of Leaf to be Fed
Age of the
W orms
Multivoltine X
New Bivoltine Hybrid
Bivoltine X
Bivoltine Hybrid
I
II
III
2-2.5Kgs.
6-7.0Kgs.
25 - 30.0 Kgs
2.5-3Kgs.
8.0-9Kgs.
35.0 - 45 Kgs
CHAWKI REARING 25

The main advantage of chopped leaf is to facilitate even distribu-
tion of feed to the worms. In cold conditions chopped leaves prevent the
silkworm bed from dampness. Leaves donot curl up when the air is not and
dry.Howeveragreateramountofleavesarewastedbesideslabourexpenses.
Depending on the shape of the chopped leaves there are three meth-
odsofchoppings. Theyaresquare,oblongandtriangular.The square method
is best of all which prevents lead drying. Long thin strips or oblong shapes
are suitable when the season is wet. Chopping of leaves must be regulated
according to the condition and size of the worms. Thus the surface of the
chopped leaf is equal to the square of the length of the worms. The size of
the chopped leaf for chawki worms are given below.
Chopping of leaves is carried using chopping board and knife. Leaf
is arranged in regular layers and cut to the required size depending on the
age of the worm. All the chopped leaves are collected in a clean mat and
loosened. Then the chopped leaves are sprinkled in the tray.While cutting
the leaves care is taken not to crush or bruise the leaves
2.6.4. Frequency of Feeding
The frequency of feeding for chawki worms depends again on the
season. Generally these worms are fed four times a day. However the rear-
ingbedsarekeptcoveredwithparaffinpaper. For maintenance of humidity
in the rearing bed foam rubber pads or paper soaked in water are used.
2.7. Bed Cleaning
Silkworms are fed with largequantityofmulberryleavesthantheir
eating capacity.Thus unconsumed leaves which are unfit for food remain
in the tray at the end of each feed. Besides this excreta of worms forms a
thick bed. Out of the total weight of leaf taken as food, three fifth is
excretedandonlytwo-fifthisbeingassimilatedbythesilkworm. Thepilling
Leaf size (cm2)
instar peak eating stage preparation for moult
I
II
III
2.0
4.0
fullleafcutintofourpieces
1.0
1.5
2.0
tostartwith
0.5
2.0
4.0

of litter makes the beds moist. This releases process of fermentation liber-
atinginjurousgasesandalsofavoursmultiplicationofpathogens. Allthese
above factors are harmful to the worms. Therefore removal of old (unused)
mulberry leaves, faecal matter of silkworms, exuviae, dead or unhealthy
worms etc., from the rearing bed is called bed cleaning.
2.7.1. Frequency of Cleaning
Cleaning involves labour and frequent cleaning is not advisiable as
itcutstheeconomicsofreading. Whilecleaninglossofwormsisinevitable
especially in chawki rearing. The frequency of cleaning for young worms
areasfollows.
Iinstar — Once
IIinstar — Twicei.e.oncejustaftertheImoultandagain
beforesettingforIIMoult
IIIinstar — Thricei.e.onceaftermoult,onceinthemiddleofIII
age and once Just before setting for IV moult.
2.7.2. Methods of Cleaning
For cleaning of beds husk, nets, cut straw are used. There are three
methods of cleaning.
1. Cleaning with husk
2. Cleaning with Net.
3. Cleaning with husk and net.
2.7.2.(a). Cleaning with husk
For this method charred husk or paddy husk is sprinkled evenly
over the bed of silkworms. This sprinkling of husk is carried just prior to
firstfeedingearlyinthemorning. The worms crawl through the husk layer
toreachtheleaves.Duringthesecondfeedingthebedisreadyforcleaning.
Allthewormsarecollectedtogetherbyabrushandtransferredintoanother
freshtray.
The natural paddy husk is too big and too thick for first two ages.
Thereby the worms cannot come up. For these ages, husk should be broken
into small pieces before it is used. Care should be taken to avoid dust of
husk as it spoils the leaves fed to the worms. Formalinised charred husk
helps to avoid attack of muscardine disease.
CHAWKI REARING 27

2.7.2.(b). Cleaning with net
In this process a net with mesh suited to the size of the worms are
used.Duringtheprocessofcleaningthenetisspreadoverthebedjustprior
to the first feeding early in the morning. Then it is cleaned after second
feeding. It is very simple method and requires little labour. However it is
notconvenientforthepurposeofspacing. Themeshsizesofdifferentclean-
ingnetsare
First and second instar …………….. 2mm2
Thirdinstar …………….. 10mm2
2.7.2. (c). Combined husk and net method
In the process of cleaning both husk and net are used. First a thin
layer of paddy husk is sprinkled over the bed and a suitable net is spread.
Then after two feedings the worms are transferred along with the net into
another tray.This process is more expensive and not suitable for spacing.
2.8. Spacing
This is an important aspect which needs maximum care. Over-
crowded bed does not permit free and complete growth of the worms. It is
very important for the virorous and full growth of worms. As the worms
grow in size and weight, the bed density increases leading to crowding.
Therefore the population density in the rearing bed should be regu-
lated to ideal condition. In rearing most of the failures are because of im-
proper spacing in the bed. as the age of the worms increases the length and
breadth increases (Table2.5).
Table : 2.5 Length and breath of worms
Increaseinlength Increaseinbreath
2 ½ times that of newly
hatched worm
4-5 times that of newly
hatched worms
7-10 times that of
newly hatched worms
2 times that of newly
hatched worms
4 times that of newly
hatched worms
6-7timesthatof
newly hatched worms
Stage
I
II
III

Over crowding of worms means insufficient space for the move-
ment and free feeding of the worms. Crowded condition favours to increase
gases, head and fermentation of faecal matter. Fermentation process par-
ticularly happens during early stages when temperature and humidity are
high.Inthisconditionwormsdonotfeedfreely.Thisresultsinunequaland
unhealthy growth of larvae. The worms become weak and easily suscep-
tible to various diseases. The commercial characters are also severely af-
fected. The Table 3.6 indicates the need to expand the rearing beds from
timetotime. Thereby orderly growth of silkworm can be expected.
Table. 2.6. SCHEDULE OF SPACING
Sparse spacing of worms is not desirable as it leads to wastage of
leaves.Innormalconditionthespaceisdoubleortripledfromfirstinstarto
thirdinstar. On the whole the space has to be increased by 80 – 100 times
from brushing to ripening of worms spinning.
CHAWKI REARING 29
Age of
worms
Area required for rearing Increases
spacing during
eachinstar
To begin
with
Atthe
end
1stInstar
2nd Instar
3rdInstar
4thInstar
5thInstar
4sq.ft.
15sq.ft.
45sq.ft.
90sq.ft.
180sq.ft.
14sq.ft.
45sq.ft.
90sq.ft.
180sq.ft.
360sq.ft.
3 1/2 times
3 “
2 “
2 “
2 “
The above in terms of bamboo trays may be stated as follows :
Age of worms
Traysof31/2’
diameter Traysof4’ diameter Traysof41/2’
diameter
Trays Area of seat
ineachtray
Trays Area of seat
ineachtray
Trays Area of seat
ineachtray
2ndInstar
Increasfrom: 21/2’
x3’
(ortofill
almost the
entiretray)
1st Instar
Brushin:
Increasto:
2
2
11/2’
x1 1/2’
21/2’
x3’
2
2
11/2’
x1 1/2’
21/2’
x3’
2
2
2’x2’
31/2’
x3’
(ortofill
almost the
entiretray)
2 2 21/2’
x31/2’ 1 “
5 4 3’’
x33/4’ 3 “to: “
3rd Instar
Increasefrom:
to:
5
10
Full Tray
“
4
8
3’x3 3/4’
Full Tray
3
6
“
“
Schedule of Spacing (A)

(For100Diseasefreelayings)
Ageof
Silkworm
Temperature
0
C
Humidity
%
SizeofLeaves
(cms.)
Totalquantity
ofleaf(kgs.)
No.of
feeds/day
No.of
cleaning/
instar
Spacing(Reaing
seatfor100dfls)
(Sq.ft.)
ImprovedMultivoltineHybrids
BivoltienHybrids
I
II
III
27
27
26
80-90
80-90
80
0.5to2.0
0.5to4.0
0.5to6.0
2to2.5
6to7.0
25to30
3to4
3to4
4to5
1
2
3
4to14
15to45
45to90
I
II
III
27
27
26
80-90
80-90
80
0.5to2.0
0.5to4.0
4.0to6.0
2.5to3
8to9
35to45
3to4
3to4
4to5
1
2
3
4to14
15to45
45to90
Table:3.7.REARINGSCHEDULEOFYOUNGWORMS
30 SILKWORM REARING TECHNOL-
OGY

2.8.1. Time and frequency of spacing
Spacing should go simultaneously with continuous development of
worms. Therefore worms are spaced at each feeding. The development of
worms is most rapid in first age. Thus spacing is done frequently,anditis
always advantageous to combine spacing with cleaning. This saves labour
also. In further instars spacing is combined with cleaning. When the hu-
midity and temperature are higher than optimum then the worms are spaced.
Thetraysarekeptinalternateshelvesforfreecirculationofair.
2.8.2. Methods of spacing
The spacing can be conducted separately or in combination with
cleaning. Amongthesetwothelattermethodisconvenientandsatisfactory.
It helps in less handling less disturbance of worms.
2.9. Moulting
The silkworm larval life has five instars and four moults. The lar-
vaecastsoffitsskintoaccommodatethebodygrowth. Thisiscalledmoult-
ing. The silkworm larvae attain their maxi-mum body growth of parti-cular
instar and as a result body becomes stout, and shiny and amber coloured.
These two characters are seen in a larvae at the approach of moult-ing. In
rela-tiontothesizeofthebody,the head of the worm appears small and
dark. This is the time for bed
cleaning and wide spacing.
After them worms are about
to settle for moult are given
one or two feeds which helps
to reduce the humidity and
favours uniform moulting. In
high humid conditions a thin
layeroftimepowderisdusted.
This prevents early moulted
larva from eating, favouring
uniform growth. Feeding is
stoppedwhenalllarvaesettle
for moult. Under proper rear-
ing conditions all the larvae
settleuniformlyformoultand
come out of moult uniformly
(Fig. 3.8 a&b).
Before
After
Fig. 2.7 Moulting
CHAWKI REARING 31

The moulting time for first age is 20 hrs. second and third age lar-
vae requires one day. Moulting is a very sensitive process in the life cycle
of silkworms. After moulting fresh larvae of next instar comes our casting
theiroldskin. The worms head is bigger in relation to the body size. It is
rusty in colour, less shiny because of loose skin. The first feeding of the
new instar starts only after almost all worms pass moult. Newly moulted
wormsaredustedwithceresinlimepriortofirstfeedtopreventmuscardine.
Anyirregularityinsettlingformoultisnoticed,allsuchlatelarvae
are segregated by net feeding and reared a second batch. Care should be
taken to keep the bed dry during moult. Thisfacilitiesthelarvaetowriggle
outoftheoldskin.
2.10. Rearing methods
There are three methods or rearing but in all methods importance is
given to, the maintenance of leaf quality, humidity, temperature so as to
ensure vigorous and healthy development. The rearing methods are;
1. Paraffinpaperrearing
2. Box rearing
3. Co-operative rearing
2.10.1.Paraffin Paper Rearing
A good quality paraffin paper is used in this method. It should be
devoidofpetroleumsmell,folds,turns.Itisspreadasabottomlayerandas
a cover for rearing beds. In between the sheets on all four sides of rearing
bed, strips of wet foam rubber or news paper are placed to maintain the
required humidity. Light weights are kept on the top paraffinsheettoseal
the edges for better maintenance of rearing bed humidity.
While feeding the worms, the top paraffin paper sheet must be re-
moved 30 minutes prior to feeding. This allows supply of fresh air to the
silkworms and eliminates toxic gases accumulated in the bed. when the
worms settle for moult, paraffin paper is not necessary. Further the bed
must be dry during moult. A thinlayeroflimepowderissprinkledoverthe
bed which helps to keep the bed dry.This also prevents muscardine.

Rearing in Wooden Box,
Bamboo Tray
Paraffin Paper Rearing
Spacing using Chop Sticks
Second Instar Worms
Fig. 2.8 Chawki Rearing
CHAWKI REARING 33

2.10.2.Box Rearing
Inthismethodspeciallymadeboxesareusedforrearing. The boxes
may be with or without lids.
a). Rearing in boxes with lids
It completely resembles the paraffin paper method. After prepara-
tion of bed a lid is placed on the box and later arranged in the shelves. In
third instar lids are not necessary.When the larvae settle for moult, the
paraffinpaper, wet foams and the lids are removed to keep the bed dry.
Fig. 2.9 Box Rearing

b). Rearing in Boxes without lids
thisrearingagainresemblesparaffinmethod. The wooden boxes of
uniform size with 10-15 cm deep are used. After preparing the rearing bed
the boxes are piled one over the other for rearing first instar. For rearing
secondandthirdinstarlarvae,aspaceof2-3cmbetweentheboxesismade
forventilation. Theboxesarekeptopenforatleast30minutespriortoeach
feeding. It must be completely open when larvae start settling for moult.
Care must be taken to disinfect the worms to prevent muscardine.
2.10.3. Co-operative Rearing
Rearingofsilkwormsrequirestechnicalskills. Theseskillsarelak-
inginmostofruralfarmers.Ifthesilkwormsarenotrearedproperlyinthe
young stages they are proned to diseases in later instars, resulting in crop
failures.Besidesthisrearersarenotabletoafford the necessary equipment
for silkworm rearing under ideal conditions. In order to overcome all these
problems co-operative rearing have been orgnaised to provide technical
assistance,ideaconditionsetc.therearingisconducteduptosecondorthird
moult. These are also called as chawki rearing centres. These centres are
provided with ideal rearing houses with all the necessary equipment. The
total rearing are supervised by technical experts. Mulberry leaf for rearing
is provided form a single garden which ensures uniform quality of leaf.
Because of ideal conditions and quality leaf silkworm growth is
vigorous and healthy.This ensures good crop results and income to the
CHAWKI REARING 35
Fig. 2.10. Co-operative Rearing

Fig.2.11.Co-operativeRearing
rearer.The silkworms are reared in large scale reducing the expenditure
whichischargedtotherearer.furthertherearerneednotbotheraboutchawki
rearing and is free for a fortnight period. Generally co-operative rearing
centres have a capacity to rear 200 to 500 boxes (each box contains 20,000
eggs)uptothirdmoultorboublethesizeuptosecondmoult.Itispopularin
Japan and 90 percent rearings upto third moult are carried in co-operative
centres. After then, worms are be distributed to individual rearing farmers.
A. Advantages
B. Stagewise labour requirement
C. Breakup of the cost of rearing
D. Types of Co-operative rearing

CHAWKI REARING 37
Fig.2.12.Co-operativeRearing

1. It ensures stable rearing conditions and high cocoon quality
2. it saves labour and leaves time for other work.
3. it reduces expenditure and lowers cost of production
4. disease control can be carried out more effectively.
SUMMARY
§ Rearingoffirstthreeinstarsiscalledchawkirearing. Theselar-
vae are resistant to high temperature and humidity and grow
well ensuring good cocoon crop.
§ The worms grow very fast and requires nutritious leaves. The
total weight of the worm is attained in chawki rearing.
§ Larvae are very sensitive to diseases and requires to be reared
carefully.
§ Chawki worms are fed with quality leaf.
§ There are two leaf selection methods. They are glossy leaf
method, lenticel and bud method.
§ Silkworms do not eat withered leaf. Leaf preservation is neces-
sarytoprotectthenutritivevaluesfromtimetotime.Leavesare
to be stored in leaf chamber or earthrned pots.
§ The aim of feeding worms is to satisfy their appetite. Proper
feeding enables healthy growth of worms. However growth de-
pends on the amount of mulberry ingested and digested.
§ The worms are fed with chopped leaves according to their age.
Feed is given four times a day.
§ Bed cleaning enables to remove waste leaf and excreta.
§ Bed cleaning is carried using husk, net,husk & net.
§ Cleaning nets of 2 and 10mm2
are used for bed cleaning.
§ Spacing of worms facilities proper growth.
§ Care should be taken during moulting of worms as it is an im-
portant stage of larval development.

§ Chawki rearing is carried in three methods. i.e. covered rearing
with paraffinpaper,boxrearing,co-operativerearing.
§ Depending on the available conditions the method of chawki
rearing in adopted. However the best method is co-operative
rearing.
QUESTIONS
I. SHORT QUESTIONS
1. Define chawki rearing
2. Mention temperature and humidity requirements of chawki worms.
3. Which mulberry leaves are suitable for chawki worms ?
4. What is glossy leaf ?
5. Mention popular method of leaf selection.
6. Mention leaf selection methods.
7. Mention leaf preservation equipments.
8. What are the methods of leaf chopping ?
9. What is the frequency of feeding chawki worms ?
10. Define bed cleaning.
11. What is the frequency of bed cleaning in chawki rearing ?
12. Mention methods of bed cleaning.
13. When do you clean silkworm beds ?
14. Define spacing.
15. Define moulting
16. How do you identify moulting worm ?
17. What is the use of paraffinpaper?
18. Name methods of chawki rearing.
19. How many instars are there in larval stage ?
20. What is the food of silkworms ?
CHAWKI REARING 39

II. ESSAY QUESTIONS.
1. Discuss importance of chawki rearing
2. Discuss the environmental conditions required for chawki rearing.
3. Discuss about the importance of quality leaf in chawki rearing
4. How do you select mulberry leaves for chawki worms ?
5. Describe the importance of leaf preservation.
6. Describe feeding aspects of chawki worms.
7. Describe different methods of bed cleaning.
8. W rite about the importance of spacing in chawki rearing
9. W rite about the care during moulting.
10. Describe methods of chawki rearing.
11. W riteshortnoteson
a. Spacing b. Leaf chopping
12. W riteshortnoteson
a. Leaf preservation b. Moulting

3
LATE AGE REARING
3.1. INTRODUCTION
Rearing of fourth and fifth instar worms is called as late age worm
rearing. These wroms require less humidity and preferable low tempera-
ture. This stage is the real feeding stage. The worms consume about 90 to
95 percent of the total feed. When chawki worms are reared perfectly, late
age rearing is comparatively easy.As this is the final stage of rearing, worms
are fed proper with quality leaves to get good crops.
3.2. IMPORTANCE OF LATE AGE WORM REARING
The fourth and fifth instars of silkworms are more delicate and re-
quire rigid conditions of temperature and humidity. During these stages the
worms activity and develop silk glands and secrete silk, but also stores the
food for coming series of metamorphosis. Therefore these worms are fed
with quantity leaves. These worms eat mature leaves which contain less
moisture. During this period silkworm body volume increases by 29 times,
body weight by 25 times and silkgland weight by 200 times. Thus rearing at
these stages influences quality and quantity of cocoon crop production.
3.3. ENVIRONMENTAL CONDITIONS
The ecological and nutritional conditions required for late age are
completely different from young age. The ecological factor greatly influ-
ences the growth of the worms.
3.4. Temperature
The adult silkworm is susceptible to high temperature. The larval
mortality increases when young worms are reared in low temperature (240
C)
and late age rearing in high temperature (280
C). temperature influences to
alter various physiological aspects which intern reflects on silk characters
and production. Therefore wide fluctuations of temperature should be
avoided. The optimum temperature required for late age worms are;
Stage of Worms Optimum temperature
IV
V
240
- 250
C
230
- 240
C

3.3.1.a. Regulation of Temperature
When the temperature in the rearing room rises to 300
C and above,
it affects the survival rate, pupation and commercial characters. In tropical
areas it is very difficult to maintain ideal temperature. Therefore it is neces-
sary to set up protective fixture from the heat. If the rearing room is roofed
with zinc or tiles, it is desirable to have insulating material i.e.. foam styrol.
This insulation prevents high reise of room temperature. If insulation ma-
terial is not available temporary ceiling is advisable. Trees also planted
around the rearing room. If there is no scarity of water, water sprinkles on
the roof works well. Daily variable temperature within a range of 25± 40
C
is preferable over constant temperature.
3.3.2. Humidity
Late instar worms are sensitive to high humidity. The humidity
requirements during feeding and moulting are quite different in silkworm.
The optimum humidity required for IV and V instars is 75% and 70%
respectively. During feeding high humidity is maintained which favours to
keep the freshness of leaves fed to silkworms for sufficient consumption.
During moulting process maintenance of low humidity is preferable.
Fig. 3.1 Distribution of Temperature in rearing room

LATE AGE REARING 43
3.3.3. Air
The air in the rearing room is polluted by carbon monoxide, CO2
,
NH4
, SO2
,. These pollutants are produced by working men, silkworms,
mulberry leaves, fermentation of leaves, burning of charcoal. After finish-
ing the daily rearing activities such as feeding, cleaning, spacing generally
the room is closed, or poorly ventilated without knowing its effects. Then
the injurious gases increase to a significant level and affect the worms.
Therefore windows should be wide open to improve the air current. The
growth of the silkworms and air current are correlate, Carbondioxide con-
tent exceeding one per cent in the rearing room is bad for silworms. During
high temperature, the CO2
released by silkworms increases in proportion to
the humidity. Air current of 1.0 meter per second during V age rearing con-
siderably reduces larval mortality. Further it improves ingestion, digestibil-
ity, larval weight, cocoon weight and pupation rate.
3.3.4. Light
Rearing of silkworms in continuous light delays growth. Further it
causes pentamoulters and reduces both larval and cocoon weights. Silk-
worms are fond of dim light of 15 to 20 lux and avoid strong light and
darkness. Late age worms thrive better in 16 hours light and 8 hours dark
periods.
3.4. QUALITY OF MULBERRY LEAF
The details of quality of mulberry leaf are described in chapter 3.4.
From the quality point of view late age worms are fed with bottom
mature (dark green) leaves which are thick, soft, rich in protein, compara-
tively low moisture leaf. Too tender or over matured leaves are not fit for
feeding. However they feed on wilted, dusted, bad leaves and over matured
and less nutritive leaves. But this results in slow growth and become sus-
ceptible to diseases. If they reach spinning stage, it results in poor quality
cocoons. From the 3rd
day of the 5th
stage the silk glands of the warm de-
velop vigorously. Therefore they are fed with abundant good quality mul-
berry. In the late age worms the amount of mulberry ingested and digested
increases. However the ratio of digestion is lower than young worms.
In the spring, when are temperature falls suddenly at night, silk
worms fell ill and cannot digest the mulberry. Therefore it is necessary to
raise the temperature. The dose of mulberry is increases slightly in the morn-
ing feed in the day time when it is warm. But feed dose is decreased is the
evening.
3.5. LEAF SELECTION
Mulberry for late age worms are also selected by largest glossy leaf
method which is described in chapter 3.5.

In glossy leaf method selection, the mature leaves remained on the
mulberry twigs after chawki rearing are fed to IV and V instar worms pluck-
ing from top to bottom.
3.5.1. Leaf Preservation
Leaf preservation is more important to prevent withering of leaves.
It is suitable to preserve late age worm leaves in leaf chambers. In dry
further lost by rapid evaporation after harvest. Therefore it is necessary to
reinstate moisture into the leaf by sprinkling water over the leaves and
preserving under wet gunny cloth or leaf chamber. However it is ensured
that feeding the leaves should not carry water droplets. Withering of leaves
can be prevented by increasing humidity of rearing room. But it is detri-
mental to the health of late age worms. Therefore it is necessary to prevent
moisture loss without increasing the humidity by adopting proper method
of preservation.
For other details on leaf preservation refer chapter 2.5
3.6. FEEDING SCHEDULES
3.6.1. Feeding
The importance of feeding and growth of the worms are detailed in
chapter 2.6
3.6.2. Preparation of leaves for feeding late age worms.
Chopping of leaves for feeding is not essential to late age worms.
Feeding of leaves depends on leaf harvest. In case of leaf plucking whole
leaf can be given to IV and V instars. However in rainy season depending
on the humidity, leaf can be cut into two before feeding the worms. In case
of shoot harvest they are cut to a convenient size to accommodate in the
rearing tray. The quantity of leaf required for rearing 50 laying or 20,000
eggs from IV to V instar are given in table 3.
Table 3.1. Leaf requirements
Quantity of Leaf to be Fed
Age of the
Worms
Multivoltine X New
Bivoltine Hybrid (CB)
Bivoltine X
Bivoltine Hybrid
I
II
75 - 85 Kg
600 - 625 Kg.
105 - 125 Kg
700 - 725 Kg

3.6.3. Frequency of Feeding
It mainly depends on the season. Generally the late age worms are
fed four times per day i.e. 5 am, 11 am, 4 pm and 10 pm. Further it is
necessary to reduce the frequency in rainy season and to increase in sum-
mer. However care should be taken to reduce or increase much to the total
quantum of feed.
Fig. 3.2. Change in larval body water content
Fig. 3.3. Feedung of late age worms
LATE AGE REARING 45

Fig. 3.4. Late age Worms
V Instar
IV Instar
3.6. BED CLEANING
It is a process to remove waste and harmful material found in the
rearing bed. bed cleaning is done daily during IV and V instars. In branch
feeding, shoot feeding and individual leaf feeding they are cut to a small
size before feeding. Generally bed cleaning is preferable after first feeding.
The net size of 20mm2
is spread prior to feeding. The bed cleaning is done
before the second feeds where the worms alont with net and leaves are
transferred into afreahs tray. The faecal material and left over laeaf are put
into manure pit. While cleaning attention should be paid to keep the rear-
ing room, floor and premises clean and tidy.
Methods of cleaning are described in chapter 2.7.

Fig. 3.5. Bed Cleaning
Fig. 3.6. Spacing
LATE AGE REARING 47

3.8. SPACING
Spacing of worms in he beds play a vital role for the success of
silkworm crop and improvement of cocoon quality. Buding IV and V in-
stars more than 93 per cent total feed is given. Besides all precautions taken
while feeding of the worms by adequate leaves, crowded condition leads to
under nourishment and uneven development of the worms. Further it favours
the incident of disease and yield of inferior quality cocoons (Fig. 3.6.).
Over spacing leads to leaf wastage and higher leaf cocoon ration.
Therefore optimum spacing based on the growth of different instars is nec-
essary (Table 3.2.a,b) to get good crops.
Table 3.2.a. Length and breadth of the worms.
Increase in length Increase in breath
13 - 15 Times that of
newly hatched worms
23 - 27 - do -
10 - 13 times that of
newly hatched worms
17 - 22 -do-
Stage
IV
V
Table 3.2.b. Schedule of spacing
Trays of
31/2’ dia
Age
Area of seat
in each Tray
IV
Increase
from
to
V
increase
from
to
Tray
Trays of
31/2’ dia
Trays of
31/2’ dia
Area of seat
in each Tray
Trays
Area of seat
in each Tray
Trays
10
20
20
40
Full Tray
Full Tray
Full Tray
Full Tray
4
8
15
30
3’x33/4’
Full Tray
Full Tray
Full Tray
3
6
12
25
2’x2’
31/2
’x2’
31/2
’x2’
31/2
’x2’
Spacing should be increased simultaneously with the growth of the
larvae. It is better to space the worms while bed cleaning. The late age
worms are spaced every day.

V Instar Feeding
Disinfection
Fig. 3.7. Late Age Rearing
3.9. MOULTING
For the details of importance of moulting see first para of chapter.
2.9.
The fourth and last moult of silkworm is characteristic. The dura-
tion of moulting is prolonged when compared to first three moults. When
the conditions are optimum the moulting is completed in 30 hours. When
the worms are settling for moult, the bed is spread to a thin layer. This
spreading enables to dry the left over leaves and also provides low humid-
ity. If the rearing room humidity is high, a thin layer of lime is applied after
the last feed.
3.10. REARING METHODS
There are three methods of rearing
1. Shelf rearing
2. Floor rearing
3. Shoot rearing
LATE AGE REARING 49

3.10.1. Shelf Rearing
Bamboo rearing trays are arranged in tiers on rearing stand for rear-
ing and is called shelf rearing. The stands are arranged in rows leaving a
convenient space for attending cleaning, feeding. Generally round bamboo
trays are used for this method. In each stand ten trays are arranged. The
worms are fed with individual leaves. Four or five feeds are given per day
and nets are used for cleaning.
Advantages
1. More worms can be reared in a limited area.
2. An overall view of all the trays is possible
3. Required air and light are available.
Disadvantages
1. More labour are required
2. Care should be taken for proper spacing
3. Cost of production is more.
Fig. 3.8. Shelf Rearing

3.10.2. Floor Rearing
The rearing is carried on fixed rearing seats. The seats are arranged
in two or three tiers. Three seats can accommodate as many worms as pos-
sible. Rearing seat should measure 1-1.5 m, width and 5-7 length with a
space of 0.6-0.8m between the tiers. The length can be adjusted according
to the length of the room. There must be suffiecent space all around the
seats for attending various rearing activities. The seats are made of wood or
bamboo. The worms are fed with individual leaves or branches cut to small
size. The number of feeds are three or four in a day are adopted and clean-
ing is carried using nets.
Advantages
1. Saving on labour expenses thus reduces cost of production
2. Saves times in feeding, cleaning, spacing
3. Cost of trays and maintenance are totally eliminated
4. More worms can be reared
5. Worms growth, disease incidence can be observed easily.
3.10.3. Shoot Rearing
It is the most economical method of all and resembles floor rearing.
The rearing seats are one meter wide and length can be extended according
to the size of rearing room. The rearing seats are arranged 20cm above the
ground. Depending on the space available two tiers can be arranged with a
gap of one meter in between the tiers. This method of rearing can be carried
outdoor. When the environmental conditions are favourable, especially tem-
perature.
The worms are supplied with big shoots. In every feed the larvae
keep moving upwards consuming mulberry leaves. Due to shoot feeding
the food is distributed in three dimensions favouring better aeration of rear-
ing beds. Thus it is possible to accommodate 50% more worms per unit
area. The rearing activities especially cleaning is much reduced. It requires
only one cleaning each in fourth and fifth instar. Ropes of convenient length
are spread parallel to each other lengthwise on the bed and after two, three
feeds when worms have crawled on to new branches, the bed is held by
ropes is rolled into loose bundles by cutting the ropes for every 2 mts.After
cleaning rolled bundles are spread on to the rearing beds. Thus labour re-
quirements for cleaning and feeding are minimized.
LATE AGE REARING 51

C. Arrangement of Mulberry Twigs in Shoot/Branch Method
A. Floor Rearing
B. Shoot Rearing
Fig. 3.9. Late age Rearing

Advantages
1. Labour requirements are reduced to 60% in IV age and
50% in V age.
2. Leaf saving is about 25% in IV age and 10% in V age.
3. Provision for indoor and outdoor rearing
4. Better aeration of rearing beds.
5. Three dimensional feeding reduces leaf wastage
6. Accommodates 50% more worms per unit area.
7. Cleaning and feeding time is minimum
8. Rearing activities are made easy.
Fig. 3.10.Spatial Arrangement of Branch Rearing
LATE AGE REARING 53

Table.3.3.RearingScheduleofLateAgeWorms(for100DFL’s)
Note:Ensurecirculationofairiftoowarmandhumid
Ageof
Silkworm
TemperatureHumidityNo.of
feeds/day
No.ofcleaning/
instar
SizeofLeaves
(cms.)
Totalquantity
ofleaf(kgs.
Spacing(Rearing
seatfor100dfls)
(sq.ft.)
ImprovedMultivoltineHybrids
BivoltineHybrids
IV
V
Atmospheric
Temperature
“
70-75
70
EntireLeaf
Entireleafor
branches
70-85
600-625
4-5
4-5
Onceinthe
morning
daily
Daily
90-180
180-360
IV
V
“
“
70-75
70
EntireLeaf
Entireleafor
branches
105-125
700-725
4-5
4-5
Onceinthe
morning
daily
Daily
90-180
180-360

Rearing of IV, V instar worms is called as late rearing.
Late age worms eats activity and develop silk glands (gland
weight) increases to 200 times).
These worms require low temperature and humidity levels. Care
should be taken to avoid injurious gases in the room.
Worms are fed with bottom mature, thick, rich in protein, low
moisture leaves.
Leaves are preserved in leaf chamber to protect nutrients.
Full leaves are fed four times a day
Bed leaves are fed four times a day.
Worms are spaced based on the growth of late age worms. Because
bad spacing favours the incidence of the disease and yields inferior
quality cocoons. On the other hand over spacing leads to wastage
and higher lead cocoon ratio. Thus spacing is carried along with
bed cleaning.
Moulting is completed in 30 hrs. when the worms are settling for
moult, the rearing bed is spread to a thin layer.
Late age worms are reared in three methods. They are shelf rearing,
floor rearing, shoot rearing.
Out of all, shoot rearing has lot of advantages. The food is distrib-
uted in three dimension and favours to consume complete leaf. Bed
cleaning spacing is very easy.
SUMMARY
QUESTIONS
I. SHORT QUESTIONS
1. Define late age rearing
2. What type of mulberry leaf is fed to late age worms ?
3. Mention temperature and humidity required for late age worms.
4. What are the leaf harvest methods for late age worms ?
5. What is the leaf size for feeding IV and V instar worms ?
6. What is the net size used to clean the bed of the late ages ?
7. What is the time required for IV moult ?
LATE AGE REARING 55

8. List out different methods of late age rearing.
9. Which method is economical for late age rearing
10. How many moults are there in Bombyx ?
11. What is the time required to complete larval period ?
12. What are the real feeding stages of larvae ?
13. What is the percent of feed consumption in late ages ?
14. Name the gases injurious to silk worms.
15. What are the light requirements for late age rearing ?
16. What is the time schedule for feeding late age worms ?
II. ESSAY QUESTIONS
1. What are the environmental conditions required for late age
rearing ?
2. Write about leaf quality required for late age worms.
3. Describe about feeding of late age worms.
4. Write about spacing of late age rearing.
5. Mention methods of late age rearing. Describe shelf rear-
ing.
6. Shoot rearing is most economical – Justify the statement
7. Write about floor rearing.
8. Write short notes on
a) Bed cleaning b) Moulting
9. Write about the important of late age rearing.
a) Shelf rearing b) Leaf requirements

4
EFFECTIVE RATE OF REARING (ERR)
4.1. INTRODUCTION
Silkworm rearing is to be carried systematically for better crop re-
sults. Rearing activities such as incubation, brushing, feeding, leaf quality,
bed cleaning, spacing are important which reflect on the quality and quan-
tity of cocoons. Above all maintenance of environmental conditions espe-
cially temperature and humidity are vital for the growth and health of silk-
worms. Any slight change may hamper the health and lead to disease and
finally death. The cocoons are the final product in silkworm rearing to get
cash returns. Thus cocoon quality and quantity are so important which re-
flect on the price fixation. Therefore it is necessary to understand about the
effective rate of rearing (ERR) and to estimate the crop results. The calcu-
lation of ERR also helps the farmer to understand and confirm the mistakes
in the rearing activity. In this chapter calculation of ERR by various meth-
ods utilizing weight and number of cocoons are discussed along with cal-
culation of good and bad cocoon percentage for the benefit of learner.
4.2. CALCULATION OF ERR
ERR is difined as the ratio between the weight of cocoons produced
and the total number of larvae at a certain instar.
Principle for calculation effective rate of rearing is as follows.
No. of cocoons harvested
No.of larvae in 3rd or 4th instar
ERR = X 100
Effective rate of rearing is calculated on the basisi of weight and
number of cocoons. The following are the principles.
Wt. of cocoons harvested
No.of larvae brushed
ERR by weight = X 100
ERR by number = X 100
Now let us calculate ERR (in both methods) on the following values.

4.2.1. Model Problem
Number Weight
1. Good Cocoons 1413 2.020 Kg
2. Flimsy Cocoons 36 0.050 Kg
3. Double Cocoons 42 0.055 Kg.
TOTAL : 1491 2.125 Kg.
SOLUTION :
Total No. of cocoons harvested = 1491
Total No. of larvae brushed = 1610
= X 100 = 92.60
For 10,000 Larvae (brushed) we can harvest 9260 cocoons.
Total quantity of cocoons harvested = 2.125
Number of larvae brushed = 1610
= X 100 = 13.19 Kg.
We can harvest 13.19 Kg of cocoons from 1619 larvae brushed
1491
1610
Wt. of cocoons harvested
ERR by weight = X 100
2.125
1610

ERR 59
Calculate yield/100 DFL in Kg on the basis of the following data.
E.R.R. = 80; No. of worms in 3rd instar = 300
SOLUTION :
No. of Larvae in 3rd instar X ERR
100
No. of cocoons harvestd =
= = 240
For 100 DFLs = 240 X 100 = 24,000
Weight of single cocoons = 1.5 gms
Weight of 240 cocoons = 240 X 1.5 = 360 gms.
For 100 DFL = 360 X 100 = 36,000 gms
= 36 Kg. Yield for 100 DFL’s
Weight of cocoons harvested from one DFL X 100
360 X 100 = 36 Kg.
300X80
100
Calculate number of cocoons harvested if E.R.R. % is 90
No. of worms in 3rd instar = 350
SOLUTION :
ERR = 90

Cocoons harvested
350
90 = X 100
No. of Larvae X ERR %
100
Cocoons harvested =
350 X 90
100
= = 315
Calculate effective rate of rearing by number and weight using the
following values.
Cocoons harvested Number Weight
Good Cocoons 1940 2.210 Kg
Flimsy Cocoons 50 0.051 Kg
Double Cocoons 40 0.046 Kg.
TOTAL : 2030 2.307 Kg.
Total number of larvae brushed = 2140
SOLUTION :
ERR based on number is calculated by substituting the values in
principle
= X 100 = 94.85%
For every 10,000 larvae 9485 cocoons are produced.
ERR based on weight is calculated by substituting the values in
principle
= X 100 = 10.78 Kg.
10.78 Kg. cocoons are harvested from 2140 larvae
2030
2140
2.307
2140

ERR 61
Calculate cocoon yield for 100 DFL with the following data.
E.R.R. = 80; No. of worms in 3rd instar = 315
SOLUTION :
ERR = X 100
No. of Larvae in 3rd instar XERR
100
No. of cocoons produced =
= = 252
For 100 DFLs = 252 X 100 = 25,200
Weight of single cocoons = 1.5 gms
Weight of 252 cocoons = 252 X 1.5 = 378 gms.
For 100 DFLs = 378 X 100 = 37,800 gms
= 37.8 Kg.
For 100 DFLs = weight of cocoons produced from single DFL X 100
378 X 100 = 37.8 Kg.
315X80
100
Calculate cocoons product with the following data
No. of larvae in third instar 375; ERR 94.
Total No. of cocoons produced
No.of larvae in 3rd instar
ERR = X 100
No. of Larvae in 3rd instar X
ERR
100
Total No. of cocoons Produced =

375 X 94
100
= = 352.5
4.2.7. Calculation of percentages of bad/good cocoons
Calculate good and bad cocoon percentages based on weight and
number with the following values.
No. of cocoons produced = 352
The percentages are calculated by weight and number
1. Bad cocoons% = X100
Weight of bad cocoons
weight of total cocoons
X100
No. of bad cocoons
No. of total cocoons
OR
2. Good cocoons% = X100
Weight of good cocoons
weight of total cocoons
OR
X100
No. of good cocoons
No. of total cocoons
4.2.7.1. Model Problem
Cocoons Types Number Weight (gr)
Dead cocoons
Double cocoons
Forforated cocoons
Malformed cocoons
Stained cocoons
Thin cocoons
Good cocoons
Total Cocoons
125
22
15
20
100
30
1240
1552
145
95
18
35
150
50
1950
2443

ERR 63
SOLUTION :
Total number of good cocoons = 1240
Total weight of good cocoons = 1950
Total number of bad cocoons = 312
Total weigh of bad cocoons = 493
Total number of cocoons = 1552
Total Weight of cocoons = 2443
Bad cocoons % by number = X 100 = 20.10%
Bad cocoons % by weight = X 100 = 20.18 %
Good cocoons % by number = X 100 = 79.89%
Good cocoons % by weight = X 100 = 79.81 %
312
1552
493
2443
1950
2443
1240
1552
SUMMARY
Calculation of ERR is essential to understand and know the
crop activity. It also help the rearer to know the mistakes which
can be rectified in the next rearing.
Rearing activity reflects on cocoon quality and quantity. Co-
coons are the final produce to get cash returns.
ERR is the ratio between the weight or number of cocoons pro-
duced and number of larvae in a particular instar.
ERR is calculated by weight and number.
Calculation of percentages of good and bad cocoons also gives
an idea on the performance of rearing activity.

QUESTIONS
I. SHORT QUESTIONS
1. Define ERR.
2. What is the importance of ERR in rearing ?
3. Write the principle to calculate ERR.
4. Write the principle to calculate good and bad cocoon percent
ages.
5. Calculate percentage of good cocoons where total number of
cocoons are 100 and good cocoons are also 100.
II. ESSAY QUESTION.
1. Calculate ERR where weight of cocoons harvested is 20 Kg
and the number of larvae in III instar are 10,000.

5
SPINNING AND MOUNTING
5.1. INTRODUCTION
The object of rearing silkworms is to get cocoons of good quality
and maximum yield. Silkworm stops feeding towards the end of fifith in-
star and starts building the cocoons. The larvae becomes transparent, shiny
and stops feeding before spinning. Silkworm spins cocoons prior to pupa-
tion so as to protect itself from external disturbances and natural enemies.
Since it is the most critical period of its metamorphosis. But man has started
silkworm rearing as a profitable crop business. The rearer is intended to get
quality cocoons so as to improve the income. But it mainly depends on the
conditions provided during spinning and mounting. If otherwise the worms
spin flimsy cocoons by wasting the silk which decreases the production,
quality and increase the cost of production. Good mountages help the rearer
to get good quality cocoons.
The cocoons are to be harvested carefully and cleaned to eliminate
bad cocoons otherwise it reduces the cost of cocoons. The productivity and
economics is sericulture should be calculated based on raw silk out put per
unit area. The cocoon quality is the main factor that decides the cost of raw
silk. Therefore farmer should select improved breeds and modern techniques
of silkworm rearing. The quality of cocoons is decided basing on shell
weight, cocoon weight, shell ratio, floss percentage, no.of cocoons per kg.
number of bad cocoons, filament length, number of breaks, denier etc. The
crop results are assessed by effective rate of rearing (ERR). All the factors
that effect the quality and quantity of cocoons are discussed in this unit.
5.2. RIPENING OF WORMS
Fifth instar worms feeding may last from five to seven days in case
of multivoltine and bivoltine worms in the topical areas, and seven to nine
days in case of bivoltine and univoltine races in sub-tropical areas. These
worms stop feeding and called as mature larvae and starts spinning the
cocoons. As the stomach contents become empty, the mature larvae be-
comes specific in appearance. They are translucent and yellowish and it is a
clear indication that the worms are fully ripe and ready for mounting. Ripe
worms should be picked in time so that all the mature worms are enabled to
spin cocoons successfully. Worms not picked in time or unduly delayed in
picking can also be mistaken as diseased worms. Worms picked much be-
fore ripening may not also spin, resulting in unnecessary crop

losses at the last stage of rearing. Mature worms normally crawl towards
the edges of the rearing tray by raising heads, in search of suitable supports
for building their cocoons. The process of picking ripe worms and putting
on the mountage for spinning is called “mounting” of worms (Fig. 5.1).
Fig. 5.1. Mature Worms
5.3. SILK GLAND
Every animal in the animal kingdom possess certain adaptations or
modifications of body organs to suit its mode of living. During this process
some may loose certain organs fully or partially and are replaced by a dif-
ferent organ. Among these animals birds and insects show remarkable ad-
aptations compared to others. The silkworm a lepidopteran insect has four
life stages, one of which is totally inactive/resting/sleeping stage. The lar-
val stage actively feeds on mulberry and grows to a maximum size by pass-
ing four moults. It is a preparatory stage where the animal stores the food
material for future life stages and also develops certain organs which can
protect the successive stages (pupa) by enclosing it. The larvae develops a
pair of silkglands which are modified labial glands, and are capable of uti-
lizing the haemolymph aminoacids for the synthesis of silk proteins. These
proteins (sericin, fibroin) are utilized by the mature larvae for spinning the
silk cocoons. At the end of fifth instar the larva stops feeding and starts
spinning the cocoons by oozing silk from the spinneret and wraps itself for
undergoing into pupa stage. The details of spinning, cocooning are given in
this unit. The detailed structure of silk gland and silk synthesis along with
properties are also discussed in the unit.

SPINNING & MOUNTING 67
The development of silk gland and its growth depends on various
factors such as environment, rearing method and mulberry leaf quality.
Among all, the nutrient value of mulberry influences the silk production.
Since cocoon is the final crop yield, must be given care for better and healthy
spinning by feeding the worms with good quality leaf.
5.3.1. Structure
Silkgland is also a kind of dermal gland derives from the invagina-
tion of the labial ectoderm. Silkgland is an important organ which produces
silk as the source of cocoon fibre. A major part of this gland lies just below
the alimentary canal. Glands are situated on the ventro-lateral sides of the
mid-intestine and the posterior ends are blind. The gland is tubular and
cylindrical in shape. At the anterior end, the two glands unite in the head
and connect with the spinneret of the labium. The gland is devided into the
anterior, middle and posterior parts. The anterior region is a straight tube
opening at the fore end into the duct and posterioly into the middle region.
This parts is not twisted and unlike the middle and posterior parts, has no
secretory function. The middle part is the largest, twisted in the shape of the
letter ‘S’. this region is again devided into three functionally different sec-
tions fore, middle and hind parts. The fore part is slender or narrow at the
starting but thickens quickly backwards. The middle part is very thick while
the hind part is thick at anterior portion and becomes slender at postrtior
part. The posterior part is very long with many windings of uniform thick-
ness, which are regulated by dermo visceral muscles and the tracheae (Fig.
5.2).
Apair of Filippi’s glands open inside the silkgland at the joint of the
anterior division of two glands. These secrete some viscous fluid.
The wall of silkgland is composed of these layers.
1. Tunica propria having gland cells.
2. Tunica intima encloses lumen of the gland.
Tunica propria is uniform in structure. Tunica intima has a thick
chitinous layer but only anterior is shed at the time of moulting.
The silkgland grows very fast from the time of hatching to the final
stage of mature larva. The growth involves swelling and increase of size of
each cell but not increase in number of cells. The number of cells in the silk
gland remains constant (1000), with the cell division having been com-
pleted during the embryonic period. But the number of cells in silkgland of
different races is not the same.

The nuclei n the cells of the silkgland undergoes much changes as
the larvae develop from the young stage to the advanced stage. The nuclei
is more or less circular in shape (freshly hatched larva) and gradually
branches out as the age increases. According to the age the cells of the silk
gland become larger and the secretory function becomes very active. Thus
intensive branching of nuclei occupies most of the intracellular space. The
oxygen for carrying metabolic activities is supplied from the tracheae dis-
tributed in the middle and posterior parts of the silk gland though anterior
part has no tracheae.
When freshly hatched larvae start feeding on mulberry, the colour
(yellow) pigment from the ingested mulberry leaves passes towards the
alimentary canal and later into haemolymph. In the fifth instar the perme-
ability of silk gland changes and the pigment permeates into its cells whereby
silk glands become coloured. It is believed that the silk glands of the larvae
which produce white cocoons do not become coloured because the intes-
tine of these larvae do not allow the permeation of the yellow and cocoon
fibre pigments.
Fig. 5.2. Silk Glands

5.4. PROCESS OF SPINNING
When ripe worms are mounted on the mountages they passout last
excreta in semi-solid condition. When the humidity is high, excess body
moisture is also eliminated as urine. After defaecation the ripe worm starts
spinning the cocoons by selecting a suitable place in the mountage. Each
silkworm develops a pair of silkglands which synthesize silk by utilizing
the aminoacids coming from mulberry leaf. The ripeworm anchors itself
first to the mountage by oozing a tiny droplet of silk fluid which immedi-
ately hardens and sticks to the mountage. Then by swinging the head con-
tinuously the silk fluid is drawn out to form a long filament which becomes
hard. The silkworm first lays the foundation for the cocoons by weaving a
primary web. This web becomes the foothold for the larva to spin the com-
pact shell. The silkworm larvae moves its head in the shape of “or” “8” to
spin the cocoon. The former shape is found in the outer layers of cocoon
shells while the later type is usual in middle and inner layers. In this way
the larvae forms layers of silk filaments around itself and finally wrapped
in a compact shell (Fig. 5.3.)
The first formed filament i.e. primary web constitutes the floss of
the cocoons and is not reelable. The floss in uni and bivoltine races is about
2 percent of the weight of cocoon. While in multivoltine more than 10
percent floss is seen. The process of spinning continues about 1 to 2 days in
multivoltines and 2 to 3 days in uni/bivoltines. After the compact shell of
the cocoons is formed the shrinking larva wraps itself in palade or gossa-
mer layer. Finally the larvae detaches itself from the cocoons shell to trans-
form into pupa or chrysalis. This layer (gossamer/palade layer) does not
form part of main shell. It is not reelable and contributes to waste silk con-
tent.
Fig. 5.3 Spinning Stage

5.5. MOUNTAGES
Depending on the material and structure of the cocooning frames
the number of bad cocoons may increase or much labour may be required
in mounting. The details if different mountages are given in chapter-3 of
paper I. the features of good mountage are as follows.
-- Mature worm can be easily induced to cocoon spinning
-- Total mountage space can be efficiently used.
-- Manufacturing can be easily and cheaply undertaken.
-- Durable structures.
-- Storage requires little space.
-- Floss attached to the mountage can be easily removed
-- Material used is resistant to high moisture or wetness.
5.6. MOUNTING
Mature silkworms are collected and mounted on the mountages.
This laborious job requires lot of skilled labour. The ripe worms are identi-
fied and picked by skilled labour and mounted on the mountages. This kind
of mounting reduces the density of the mounted worms and incidence of
double cocoons. Diseased worms can also be eliminated. Worms can also
be mounted using nets or green branches. Branches of green leaves are
placed over the rearing bed and when the worms crawl on to them, they are
taken out and shaken over a mat, dislodged worms are put on mountages.
Similarly a net is placed over the bed after feeding mature worms, which
are no longer feeding crawl upon to the nets are collected for mounting as
in branch method. In shoot rearing early maturing larvae (10-20%) are picked
by hand and later remaining worms are collected by shaking the branches
and later mounted.
5.6.1. Proper time of mounting
It has a negative effect on cocoon quality and quantity if mounting
does not take place at the right times. When immature worms are mounted,
they die in the cocoon or their silk content in the cocoons will be low,
resulting in bad reliability. If the worms are over mature, silk will be wasted.
All these cases results in thin, double, stained cocoons which contributes
to reduce cocoons quality in terms of reliability, fiber strength, colour etc..
These defects can be eliminated by ensuring the following.

-- Silkworm body shape should be short and fat.
-- Thorasic segments should be translucent.
-- Faeces should be greenish, soft and irregular in shape
-- The worms should raise their head, thorax and should ooze
out silk from their mouth parts.
-- They should crawl around the rearing bed to find a place suit-
able for cocooning.
5.6.2. Methods of mounting
1. Picking-up mounting
When one third of body of the silkworm becomes transparent, worms
are picked-up and put on the mountages. This method helps the
rearer to mount the worms at right time. But labour expenses are
high. Generally silkworms mature between 10 am and 30 pm. The
worms become overmature producing cocoons of poor quality if
the labour is inadequate.
2. By shaking the shoots
It is better for shoot rearing. When worms (5-10%) mature, they are
picked up by hands for mounting. The remaining worms are left till
maturity. When 40-50 per cent of the worms have matured paper,
vinyl etc. may be placed on a mat and mulberry shoots full of silk-
worms are shaked. These worms are mixed with faeces and remain-
ing mulberry leaf. Then these are covered with 2-3 layers of straw
nets. After a lap of 30-40 minutes silkworms crawl upon to the net.
These worms (roughly hundreds) are mounted on selected
mountages.
Rotary mountages are leaned against the wall by putting 130-140
worms on each frame. More number of worms are put in the top frame than
the lower frames so as to fill all the frames evenly when suspended.
In another method news paper is spread on the floor, lying the
cocooning frame on one side with the entrance horizontally placed. A cer-
tain number of silkworms are put into each frame. The silkworms first fall
on to the new paper but crawl on to the frame within 30-40 minutes. Then
frames are lifted to hang (Fig 5.4.a,b).

--- Even size cocoons
--- Less floss
--- No chance for double cocoons
--- Less labour expenses
3. Net Method
A net is placed after feeding the silkworms. Mature (ripe worms)
crawl onto the net while others feed. The net is taken along with
worms for mounting.
4. Branch Method
It is similar to net method where only mulberry shoots are used.
When worms crawl onto shoots are mounted.
5. Self-Mounting
First mature worms are picked by hand then a self-mountage frame
is hanged very near to silkworm beds. Ripe worms crawl onto the
mountage frame. Which is later lifted to hang. It reduces labour
cost.
Fig. 5.4. Mountages
Zig Zag Mountage
Set of Rotary Mountage

Fig.5.5.DensityofMounting
A.Normal
B.Crowded

5.6.3. Density of Mounting :
The density varies according to the size and type of mountage. The
details of density of mounting for different mountages are as follows.
Fig. 5.6. Cocoon Harvesting
S.No. Mountage Details of Density
1. Chandrika 50 worms per 10 X 10 cm
(1100 per chandrika)
2. Rotary 1500 worms per mountage
3. Centipede 350-400 larvae/m2
4. Square frame type 150 larvae per mountage

5.7. ENVIRONMENTAL CONDITIONS
Mounting and spinning are to be carried with atmost care to get
good quality of cocoons. Ideal temperature of 220
-230
C and relative humid-
ity between 60-70 per cent are required. These conditions are important
during the first 50 hrs. after mounting. Temperature above 260
C affects the
cocoon quality.
5.8. CARE DURING SPINNING
1. In the mounting room old news papers or mats are put under the
mounting frame. When urine and excreta falls on the paper it must
be removed
2. If the temperature raises beyond 220
-230
C the shell becomes very
loose and folded with wrinkles and knots. It also changes the prop-
erties of sericin. This induces cohesion of silk filaments and causes
difficulties in reeling. Low temperature slows down the secretion of
silk bave resulting in large size cocoons. Further it takes very long
time for spinning.
3. Relative humidity (60-70%) induces good health, good reelability
and quality cocoon. When it raises the larvae and pupae cease to
death. Low humidity causes double layerd cocoons, loose cocoons.
4. Excessive moisture and harmful gases are released from faeces and
urine of silkworms. Air current speed should be less than one metre
per second and fast or strong air current causes crowding of mature
silkworms resulting in excessive number of double cocoons.
5. Mounting room requires moderate, even illumination. Strong light
causes crowding of silkworms at one side and finally results in double
cocoons or uneven thickness cocoons. Complete darkness will slow
down the spinning process resulting in low quality cocoons.
6. Ants crawling on to the mountages are prevented.
7. Spinning worms if disturbed increases floss percentage.
5.9. COCOON HARVESTING
The silkworm larva metamorphose into pupa after spinning the co-
coons for about 48 hours from the time they are mounted. Generally pupa-
tion takes place on the 4th
day of spinning. Thus the worms inside the co-
coons will be still in the form of prepupa, which has a delicate cuticular
skin. Thus if the cocoons are handled before this stage, the skin may rup-
ture and body fluid will ooze and stain the cocoons, making it unsuitable

for reeling. Thus early harvesting of cocoons should be strictly avoided. In
course of time the pupal skin hardens and turns to dark brown. The co-
coons are then harvested on the 5th
day in summer and 6th
day in cooler
season. In the case of seed cocoons, they may be harvested on the 6th
or 7th
day. Harvesting must not be delayed beyond the said period. Because it
affects the reeling activity (Fig. 5.6.).
Before harvesting the cocoons, the mountage is held in a slanting
position with the cocoon side downwards and given a gentle shaking to
Fig. 5.7. Transport of Cocoons
dislodge the faecal material.
The flimsy cocoons are taken
out with forceps or chopsticks.
Care must be taken not to rup-
ture the cocoons as their body
fluid or dead silkworms may
stain good cocoons. The co-
coons harvested are kept in
thin layers in a tray or on a mat.
After harvesting, the cocoons
are first cleaned to remove pel-
lets or debris sticking to the
cocoons. Then they are sorted
to separate bad cocoons.
5.10. TRANSPORT
The cocoons should be put into cotton bags each weighing about
10kg. They are loosely packed and transported in cool hours of the day (ie.
Morning or evening). If transport in larger bags, cocoons will be steamed
or crushed. Strong vibration during transportation is harmful because co-
coons might be crushed. While transporting cocoons are protected from
direct sunlight and rain is also important.
Cocoon cost depends on the quality. Thus they are well protected
from direct sunlight and humidity. Cocoons are placed in heaps and samples
are given for quality testing, basing on which cost is decided. Cocoons are
transported to well developed areas of reeling to get good returns. The co-
coon quality is based on certain aspects like hatching percentage, ERR,
percentages of good and bad cocoons, shell ratio, denier, filament length.
All these factors influence the cost of cocoons.

5.11. TRANSPORT OF COCOONS
Transportation of cocoons is a crucial step in marketing. During
transportatiojn of the live cocoon, if care is not taken, the live pupa inside
the cocoon will be deformed, thereby oozing out the body fluid inside the
cocoon. This damages the silk fibre and discolours the inner portion of
cocoon. The inner silk layer of the cocoon gets hardened, making the co-
coon unreelable and increasing the silk waste.
Improper method of transportation often causes pressure on cocoons
and crushed cocoons get stained (Black colour) and stain the surrounding
cocoons which are not crushed. All these cocoons become unfit for reeling
and adds to wastage.
Transportation the live cocoons in a heap or in a closed bag or con-
tainer, the pupae often suffocate, resulting in perspiration. The perspira-
tion, being alkaline in nature affects the sericin layer of the cocoon filament
which results in poor reelability.
Transportation of good cocoons along with melted, flimsy, stained
cocoons. The damage is much more as the pupae inside the cocoon are
easily susceptible to melting. Finally good cocoons are stained and thereby
reducing the cost.
-- Improper transportation of live cocoons results in low
percentage of recovery of silk
-- Increase in the percentage of recovery of waste
-- Affecting the quality of silk
-- Increase in renditta
-- Increase in cost of production
-- Lower price
Immediately after harvest the cocoons are cleaned and sorted to re-
duce the percentage of defective cocoon. This also reduces the damage of
good cocoon during transport. However the cocoons are transported safely
to get good price. The following points are adopted for safe transportation.

1. Cocoons are filled in suitable containers
2. Container should be so designed to provide enough aeration, pre-
vent jolting and crushing of cocoons, prevent damage to the pupa
inside the cocoon.
3. Cocoons are filled in container at a minimum level to minimize the
pressure on the bottom layer of cocoons.
4. Perforated containers are suitable which allows good air circula-
tion.
5. Good air circulation prevents absorption of moisture by the cocoons
and denaturation of the sericin on the filament.
6. The container is covered properly so that the cocoon are not sub-
jected to the sun light.
7. Cocoons are transported in cool hours of the day.
8. Avoid delay in transportation after filling the containers.
9. Avoid transport of cocoons in an heap or in a container without
perforations.

SUMMARY
Fig. 5.8. Good Cocoons
v Ripe or mature worms are identified by translucent and yellowish
colour. These are picked in time for cocoon spinning. The larvae
are put on moutages by skilled labour.
v Crowed worms on mountages results in double cocoons.
v Selection of moutages is very important. In India chandrika is popular
and cheap mountage.
v Worm passes out last excreta before it starts spinning. The worm
first oozes a tiny drop of silk for anchoring and then draws along
filament by swinging the head continuously.
v Spinning takes 2-3 days, to wrap itself into a compact shell.
v The inner most layer (gossamer) and outer most (floss) layers are
not reelable.
v Temperature (220
-230
C), humidity (60-70%), good air current and
ventilation are required.
v Cocoons are harvested after 5-6 days of mounting.

v Sorting of cocoons (bad and good) improves the cocoons price.
v Cocoon are transported in cool hours of the day by packing in very
loose bags/baskets.
v Cocoons are protected from direct sun light and humidity.
v Cocoon assessment is calculated based on shell ratio, floss percent-
age denier, filament length etc., for price fixation.
QUESTIONS
I. SHORT QUESTIONS.
1. How do you identify ripe worms ?
2. Define mounting.
3. Name the popular mountage in India.
4. What is the best time for mounting ?
5. Mention the reasons for bad cocoon formation.
6. What are the advantages or rotary mountage mounting ?
7. Define spinning .
8. Mention methods of mounting.
9. Define floss.
10. What is palade layer ?
11. What are the temperature and humidity levels required for spinning?
12. Define cocoons harvesting.
13. Define sorting of cocoons.
14. How do you transport cocoons?
15. What are the factors that influence price fixation ?
II. ESSAY QUESTIONS
1. Detail about mounting process.
2. Explain about mounting methods.
3. Write about care during spinning.
4. Write about harvesting and sorting of cocoons.
a) Transport of cocoons b) Ripe worms
a) Cocoons sorting b) Spinning

6
SILKWORM DISEASES
6.1. INTRODUCTION
Silkworms are not exceptional to diseases and pets. It is therefore
very essential to take certain precautions so as not to allow their out break.
At the same time it is desirable to find out effective measures to cure the
silkworms once they get affected. But under measures to cure the silkworms
do not get diseases. The income in sericulture depends on the disease and
pest control. In general emphasis should be made on improving the silk-
worm strain on the aspects of health, along with excellent characters of silk.
Usually polyvoltine strains are healthy but cocoon quality is often
poor. It can be considered by attempting efforts to increase the cocoon weight
and yield. Presently bivoltine and multivoltine strains are better employed in
sericulture. The outbreak of silkworm disease is mot closely related to the
state of health of the silkworm. However, depending on the strain, the resis-
tance varies to certain diseases. Only a few strains exhibit a strong relation-
ship between disease and health but not others. Thus it is desirable to have
overall healthy silkworm.
The resistance and susceptibility of the silkworm also vary according
to the type of disease. These two aspects depend on nutritional status, envi-
ronmental conditions. Pathogenic organisms from the infected silkworms
disseminate to the rearing rooms, equipment, eggs etc. when disinfection is
not properly carried out, the infection breaks out on a large scale. The dis-
eases spreads widely if the diseased silkworms, dead bodies, excreta are not
completely removed and the premises cleared. Thus good sanitation and
healthy atmosphere favour the good health of silkworms.
The microorganisms like protozoans, bacteria, virus, fungi cause dis-
eases to silkworms. All these diseases, their pathogenic effects, preventive
and control measures are dealt in detail for the benefit of the learner.

Fig. 6.1. Sources of infections

SILKWORM DISEASES 83
Fig. 6.2. Pebrine Infection
6.2. PROTOZOAN DISEASES
The major protozoan diseases of the silkworm is the pebrine. It is a
chronic and disastrous of silkworm Bombyx mori L. It was this disease
which was responsible for the sudden collapse of the silkworm industry of
both France and Italy in1965. The name pebrine was given to the disease in
1860 by De Quatrefages because the black spots that appear on the dis-
eased worm look like pepper grains.
6.2.1. Casual Agent and Infection
Pebrine is caused by Nosema Bombycis belonging to the family
Nosematidae of order Microsporidia. Pasteur observed that the disease may
be transmitted through the egg, by contact with diseased silkworms and
though ingestion of contaminated food. Infection also results from diseased
and dead larvae, faeces of larvae, moths, diseased egg shells, larval and
pupal exuviae etc. in the rearing bed major source of infection is the faeces
of diseased, contaminated tray, seat paper and dust from infected rearing
and leaf storage rooms.

6.2.2. Life Cycle
The life cycle of Nosema bombycis Nageli includes three stages
namely, spore, planont and meront (Fig. 6.3.c).
The mature spore is oval or ovocylindrical measuring 3-4 X 1.5-
2.5m with three layers membrane. They are inner, middle and outer layers.
The sarcoplasm is stretched in the form of girdle across the width of the
spore with a pair of nuclei. The spore has a polar capsule and polar fila-
ment. Polar capsule is a sac like structure that bulges out into the spore
cavity from the anterior end. It is surrounded by the sarcoplasm and con-
nected at one end to the outer membrane of the spore and communicates
with the outside through small opening. The polar filament is more than 30
times the length of the spore (Fig. 6.3. a,b). The infection of the pathogen
can retain after three years in the dried body of the female moth, but the
spores are susceptible to desiccation and cannot survive for more than 6-7
hours.
The spores stick to the mulberry leaves and enter into the silkworm
body. The high alkalinity and potassium ions favour spores for germina-
tion. Thus the two nuclei in the spores divide into four nuclei, then diges-
tive juices act on the spores. As a result the polar filament is extruded and
soon becomes detached from the spore. The sarcoplasm along with two
nuclei creeps out as an amoebula and the other two nuclei left behind de-
generate in the spore. After then it enters into midgut tissue. Subsequently
the polar filament gets digested in the alimentary track. The two nuclei of
the sarcoplasm fuse to form a uninucleate planont. It is globular with a
strong refractive nucleus without shell, shows amoeboid movement. It
measures 0.5-1.5m and is formed in 1-2 days. These planonts pass between
the epithelial cells of the insect intestine into the haemocoel and multiply
by binary fission. Further it invades various susceptible tissues of the in-
sect, which is called “auto-infection”.
Once the planont penetrates the cell, it transforms into secondary
form after being covered by a membrane. It is now called as “meront” or
“schizont” lanonts are extra cellular where as meronts are intra cellular.
The meronts are larger in size than planonts, incapable of movements,
spherical or oval with a definite cell wall and a nucleus. The meront ab-
sorbs nutrients from host cell and grows in size. At a certain point in its

Fig. 6.3.
Growth the meront reproduces by binary fission, multiple fission or by bud-
ding. When cytoplasm of the host cell is exhausted, meronts are arranged
in parallel rows. The meront after massive proliferation fills up the host
cells and when nutrients are depleted, sporulation takes place.
B. Spores
C. Single Spore
A. Nosema Life Cycle

The life cycle of Nosema bombycis is completed in a week after
infection in a cold climate and in about four days in hot weather.
6.2.3. Symptoms
The symptoms of this disease can be observed in all the life stages
of silkworm and from important criteria for identifying the disease.
In egg stage, poor egg number, lack adequate adherence to the sub-
stratum, lack of egg uniformly, more number of unfertilized and dead eggs,
poor and irregular hatching, eggs are laid in lumps instead of closely side
by side are observed. Some times infected eggs cannot hatch out and hatched
larvae may also die. (Fig. 6.4.)
Larvae suffering from pebrine do not show any external symptoms
until the disease is for advanced. The disease takes a more acute form in
young larvae than in adult larvae. In advanced stage of the disease, the
larvae become sluggish and dull.
Larvae show poor appetite, retarded growth and development lead-
ing to unequal in size. Larvae moult irregularly and show sluggishness.
Transovarially infected larvae die before third moult but those which are
Fig. 6.4. Pebrine Symptoms (A-Eggs; B&C-larvae)

heavily infected die during first instar itself. Larvae move slowly and ap-
pear paler and more translucent than healthy larvae. The larval body shows
wirnkled skin with rustiv brown colour and in the moribund stage they do
not rot but remain rubbery. The affect gut becomes opaque and the silk
gland shows white pustules in different places along its length (Fig. 6.5).
In acute cases larvae show irregu-
lar dark brown or black pepper
like spots on the skin. When the
larvae rest, their heads, instead of
being held up hand down. The
appearance of black spots is due
to the presence of parasite in the
hypodermal cells of the skin and
as a result the hypodermal cells
die, exhibiting melonosis as dark
pepper. A severly affected larva
may die before spinning or may
spin poor, flimsy cocoon. But af-
ter then larvae spits silk and
wastes it. Such larval body parts
show numerous oval shining
pebrine spores, which is a sure
sign of the disease.
The infected pupae are flabby
and swollen with lusterless.
Black spots are noticed near the
rudiments of the wing and ab-
dominal area. Highly infected
pupae fail to metamorphose into
adults.
The moth emergence is delayed and improper. The moths show
clubbed wings. Discolouration of scales may be seen on the abdominal
area and rarely black round spots are seen on the abdomen and wings. The
scales from wings and abdominal area easily come off. The wings do not
stretch fully with distored antennae. The egg laying capacity is poor. if the
Fig. 6.5. Pebrine infected silk gland

accessory glands are infected the moth may lay eggs with less gluey sub-
stance resulting in detachment from the egg cards (Fig. 6.6.).
Pebrine spores can be identified in mother moth after oviposition
by crushing the female moth and examined under microscope with a mag-
nification of 600. Pebrine spores appear as shining oval bodies.
6.2.4. Prevention and Control
Production of healthy eggs, is a must so as to avoid embryonic in-
fection. This can be achieved by conducting mother moth examination. It is
essential to surface disinfect the laying in 2 percent formalin for 10 minutes
before incubation. This process though be carried in grainages, must be
repeated after release of eggs from cold storage as also by farmers. If the
eggs are in advanced stage of embryonic development surface disinfection
is carried with 1 percent formalin for 5 minutes. The room and equipment
must be washed and disinfected before incubation. The other preventive
measures are maintenance of good sanitation, hygienic rearing, frequent
and careful inspection of stocks foe signs of infection, destruction of dis-
eased material and disinfection of rearing rooms and appliances. Dead eggs,
dead larvae, dead pupae in the cocoon, dead moths, litter of larvae from
infected trays, exuviae of infected larvae should be removed and destroyed.
Fig. 6.6. Pebrine infected moths

Young silkworms should be reared under hygienic conditions. As a
precaution test examination of unhatched blue eggs, dead eggs, hatched
larvae (Fig. 6.7) and egg shells can be carried out and if pebrine is detected
such lot must be destroyed. Infected silkworms, faeces and mulberry field
pests are important sources of infection and should be properly disposed of
to prevent cross infection and spread of the disease. Besides all the above
detailed preventive measures the rearer must also concentrate on resistant
area.
6.3. Bacterial Diseases
Bacterial diseases affecting silkworm are collectively known as
flacherie due to the flaccid nature of the diseased larvae. Pasteur separated
flacherie from other silkworm diseases and attributed the diseases to mi-
crobial or infectious causes. This diseases is due to rapid multiplication of
a large number of certain kinds of bacteria in the intestine, the digestive
functions of the gut are affected giving rise the disease. The other reasons
are high temperature, high humidity and bad ventilation, bad leaves, wet
and fermented leaves, over feeding, decreased alkalinity of the gut, over
crowding, poor disinfection, accumulation of faeces in the rearing trays,
improper handling etc. Bacterial diseases of silkworms are divided into
three major types i.e.. bacterial septicemia, bacteria diseases of the diges-
tive tract and bacterial toxicosis.
Fig. 6.7. Pebrine Detection

6.3.1. Septicemia
It is condition in which bacteria multiply enormously in the blood
(heamolymph) of larvae, pupae and moths.
A. Causal Agent and infection
This disease is caused by the multiplication of a large number of
bacteria in the haemolymph. The pathogens are small bacilli, Streptococci
and Staphylcocci. The infection is through injury or wounds in the skin.
Pupae and moths which do not feed are also affected with septicemia. The
black thorax septicemia is caused by Bacillus sp. Belonging to the family
Bacillaceae. The other red septicemia or serratia septicemia is caused by
the bacillus Serraia marcescens. The former is more resistant to disinfec-
tants than the latter except for lime emulsion.
B. Symptoms
The worms show some common symptoms like sluggish move-
ment, decreased appetite, straightened body, swollen thorax, shrinkage of
abdominal segment, vomiting and bead like faeces and loss of clasping
power of legs. Then the body becomes soft and discolored and the body
wall ruptures easily emitting foul smelling fluid. When a silkworm is in-
fected with more than one kind of bacteria, the symptoms are determined
by the predominantly propagated one. There is no much difference between
healthy and diseased larval body until it dies. When the larvae vomit fluid,
the body shrinks. Further soft and liquid like excrements irregular inshape
may be found. The colour of dead larvae varies depending upon the kind of
bacteria. However many larvae become black or grayish black in colour. In
general the infected dead larvae shows swollen fore-intestine shrunken
posterior part. In case of black thorax septicemia, the blackening starts
form the thorax and extends to the dorsal vessel till the whole body softens
with a slightly reddish tinge. In any case, the septicemia are generally acute
diseases, spreads quickly. The time between infection and death at 280
C is
round 10 hours. But in higher temperature the disease spreads quickly.

C. Prevention and Control
High temperature and humidity are most favourable to the propaga-
tion of bacteria. Thus rearing under these conditions should be avoided.
The disease is transmitted mainly though a injury or wound. The infected
of diseased worms should be isolated from healthy ones and destroyed by
burning or burying deep in the soil.
Effective maintenance of hygienic conditions during rearing are con-
sidered as best method to control the disease. Disinfection of rearing room
and appliances with 2% formalin must be carried out after rearing is com-
pleted. Care should be taken to avoid injury to the worms, overcrowding
and accumulation of faeces in the bed.
Fig. 6.8. Septicemia affected larva (early, late age)

6.3.1. Bacterial Disease of Digestive Tract
This disease is also know as transparent disease due to the mul-
tiplication of bacteria in the digestive tract leading to swelling and trans-
parency of the dead.
A. Causal Agent and Infection
The Causal agent of the disease is non-specific. The common bac-
terium associated with this disease is Streptococcus sp. Belonging to the
family streptococeae. It is round 0.7-0.9 m in size and are found joined by
group of two or more togive a beaded appearance. Under poor nour-
ishment and adverse environmental and rearing conditions, the physi-
ological function of the digestive tract is disturbed. It is because the sterilizig
power of the digestive fluid weakens. As a result the bacteria devoured
along with mulberry leaves, multiply in large number in the digestive
tract. The bacteria takes nutrition from the body of the silkworm, destroy-
ing the membranous tissue of the intestine. Besides Stretococcus some short
and large bacilli were also found to cause disease.
Fig. 6.9. Transparent head disease

B. Symptoms
The symptoms differ depending on the time of occurrence, kind of
bacteria found indigestive tract, the silkworm race. The general symptoms
are poor appetite, sluggish movement, transparent head, stuned body size,
slow/retarded growth, inelasticity of skin, softening of body and some times
with oral and anal discharges (Fig. 6.9). these are the symptoms of all
flacherie affected worms but the time of infection and the progress of the
disease also show certain features which are characteristic of each type of
the disease.
1. Shrinking after moulting: the larva does not feed after moulting
and body shrinks.
2. Shrinking: The larva body shrinks since it does not feed.
3. Diarrhoea : The fourth and fifth instar larvae pass soft exrements
of irregular shape. In later stage the faeces contain intestinal
membrane.
4. Vomiting : Larvae vomit and pass loose faecal matter (diarrhea).
Then body softens, putrifies and shrinks as the time passes.
The sick worms often hide under the mulberry leaves. In late stage of
disease attack the worms remain in the spinning stage without spinning till
they die.
The weakness of silkworm is the main source of infection thus
healthy and strong silkworms are selected for rearing. Incubation of eggs
and rearing should be carried at required temperature and humidity condi-
tions. Feeding of proper type of nutritious leaf, maintenance of hygienic
condition in rearing beds and culling out of diseased worms may prevent
and reduce the disease. Chloramphenical along with diet found to be effec-
tive for improvement.

6.3.3. Sotto
It is called as bacterial toxicosis.
The disease is caused by different strains of Bacillus thuringiensis
belonging to family Bacillaceae of the order Eubacteriales. The pathogen
has a vegetative, cytocyst and spore form. The spore produce delta endot-
oxin. Generally infection is preoral and can also take place through wounds
or injury. After entering into the silkworm body the toxic crystals are dis-
solved in the alkaline digestive fluid. Then the toxic substance is absorbed
through the gastric wall. It affects the nervous system, causing spasm and
paralysis.
B. Symptoms
The diseased larvae suddenly loose appetite and exhibit the symp-
toms of convulsions, sluggishness, lack of skin tension followed by shrink-
age of the body, lifting of head, spasm, tremors, paralysis, distress, consti-
pation, shrinkage and diarrhea, loss of clasping power of proleg, sudden
collapse and death. The corpse is out stretched, hard to touch and the head
appears hook shaped (fig. 6.10). The larval body becomes dark brown and
the internal organs are liquefied. The rot larvae exudes foul smelling, dark
brown colour, substance.
Fig. 6.10. Sotto disease affected larvae

The bacterial is found in the dead diseased larvae, diseased larvae
found in mulberry leaves. The pathogen is found in air and water also.
Prenvention of swallowing of toxic substance by the larvae would be a
better method, to control the disease. Infected, symptomatic, diseased, ill-
healthy larvae must be removed from the bed and destroyed. Maintenance
of healthy and hygienic conditions prevents the incidence of the disease.
Disinfection of rearing room and equipment must be carried out before
starting the next rearing.
6.4. VIRAL DISEASES
These micro-organisms cause 70 percent damage to sericulture in-
dustry. Virus disease of silkworms comprise inclusion and non-inclusion
types. The former includes Nuclea Polyhedrosis and Cytoplasmic Polyhe-
drosis while the later has infectious flacherie.
6.4.1. Nuclear Polyhedrosis
This disease is also known as Grasserie, Jaundice, Milky disease,
Fatty degeneration and Hanging disease.This serious disease occurs through-
out the year.
The disease is caused by Borrelina bomycis virus belonging to the
family Baculoviridae (Fig. 1.11). The virus multiplies and forms polyhedra
in the nucleus of the tracheal epithelial cells, adipose tissue cells, dermal
cells and blood cells. The pathogen may affect the nucleus of the middle
and posterior portion of the silkgland cells. The viral particles are rod shaped
and the size is round 330 X 80 n.m. Polyhedra vary from 3-6m. their shape
also varies, they usally have five or eight facets, although polyhedra of six
facets are the more common. The virus constitutes only 3-5 per cent of the
polyhedron.
Infection takes place through reeding of polyhedra contaminated
mulberry leaf, rarely through wounds. The disease occurs with the diges-
tion of polyhedra in the alimentary canal of the silkworm larva.

The alkaline reaction of the silkworm gut and certain enzymes dis-
solve the polyhedra, releasing the virus. The free virus passes through the
intestinal wall into the body cavity and invades the susceptible tissues. The
disease is influenced by high temperature and humidity, and their sudden
fluctutions, bad ventilation in the rearing room, ineffective disinfection of
rearing room and equipment, feeding of tender leaves during late instars,
inadequate spacing, starvation. Heat, cold and chemical treatments have
also been known to induce the disease. Surface contamination of the silk-
worm eggs is possible and can be a source of infection. It is known that the
grasserie virus reproduces very actively when the silkworm has vitamin
deficiency.
B. Symptoms
The disease cannot be identified during early stage of infection,
except sluggish nature. Initially the skin shows oily and shinning appear-
ance. In advanced stage larvae loose appetite, skin becomes thin and frag-
ile. The body becomes milky white with inter segmental swelling. The skin
is prone to rupture easily, liertaing the liquefied body contents containing
number of polyhedra which become the source of secondary contamination.
Fig. 6.11. Nuclear polyhydra

The larvae become restless and crawl aimlessly along the rim of rearing
trays, later fall on the ground and die. Generally larvae do not moult at all.
In young age larva death occurs in 4-5 days after infection. While late age
larvae die in 5-7 days. Diseased larvae hang with the head downwards.
Since abdominal legs loose clasping power (Fig. 6.12). Early infected lar-
vae die before spinning while late age infected worms spin the cocoons but
die, producing melted cocoons. The period from the swelling of the inter
segmental membranes to death is relatively short, from several hours to
less than a day. No external changes are found in pupa during incubation of
virus. But towards the end the skin ruptures easily on handling since the
pupal body is completely homogenized.
Silkworm rearing under hygienic conditions, disinfecting the rear-
ing room, appliances, mulberry storage rooms, mounting rooms, rearing
premises are to be followed. Further avoiding feeding unsuitable leaves,
proper ventilation and spacing, timely picking out and destroying the dis-
eased worms are some of the precautionary measures. Silkworms
Fig. 6.12. Grasserie affected larva

Are handled carefully not to cause any wounds. The diseased worms con-
tain number of fresh polyhedra, thus worms are removed carefully without
breaking the skin. The diseased worms, dead larvae are disposed carefully
by putting in lime pots or by burning. Extremely low and high temperature
and humidity during rearing should be avoided. Accumulation of moisture
in the rearing bed should be avoided.
Under any condition polyhedra bodies retain their infectively for
longer time. The infectivity is lost in 30 minutes at 700
C and inthree min-
utes at 1000
C. tghus it is necessary to sterilize appliances with steam or hot
water. Polyhedraal bodies present in the rearing room are inactivated by
disinfecting with formalin or high power bleaching powder. Silkworm eggs
are dipped in one per cent caustic soda solution or 2% formalin for two
minutes for surface sterilization. Then eggs are rinsed in running water for
few minutes.
Reshamkeet Oushadh disinfectant formulation containing. 1 per cent
captan, 1 per cent Benzoic acid and 96 per cent slaked lime powder gives
dual protection from grasserie and muscardine. This has to be dusted at the
rate of 2-3 grms/0.1 sq.m. area during early instars and 4-5 grams/0.1 sq.m.
during IV and V instars, once after each moult.
Fig. 6.13. Dusting of Reshamkeet Oushadh

6.4.2. Cytoplasmic polyhedrosis
This disease is found in summer season.
The disease is caused by Smithia virus belonging to the sub group
type I of the family Reoviridae. The virus is spherical, 60-7 mm in size. The
polyhedra are formed in the cytoplasm of the cylindrical cells of silkworm
larval mid gut. The polyhedra are also formed in goblet and regenerative
cells. The infection in the midgut starts from posterior portion and extends
towards anterior end. The polyhedra re 1-10 m in size, usually tetragonal or
hexagonal but rarely trigon in shape.
Infection takes place through polyhedra contaminated mulberry leaf.
Infection in the rearing trays is more common since polyhedra are released
in the excreta of silkworms. The disease outbreaks by feeding inferior quality
of leaf, high temperature and fluctuation in temperature and humidity.
B. Symptoms
Infected larvae show slow growth, stunted body, reduced mulberry
consumption and look dull white in colour (Fig. 6.13)., unequal size worms
are common and the worms show delayed moulting. Larvae loose appetite
and lag behind normal larvae in their development. In infected grown-up
larvae, the thorax becomes transparent and the body atrophies. The head is
sometimes disproportionately large. when
Fig. 6.14. CPV Affected midgut of larva

the disease advances the milky white portion advances and finally entire
gut becomes chalky white. At this stage the worm looks milky white in
colour. This larvae excrete soft whitish fecal matter containing numerous
polyhedra. Some times rectal protrusion also occurs.
The virus occluded in polyhedra can persist for more than one year
inside the rearing room, appliances and surroundings. It is resistant to for-
malin. Thus disinfection of rearing room, appliances and surroundings
should be carried using 2 per cent formalin solution and 0.5 per cent fresh
slaked lime. The dead larvae, infected worms, excreta, unused and refused
leaf should be destroyed by burning. Rearing is conducted under proper
environmental conditions. Feeding of poor quality leaves should be avoided.
Mulberry leaf sprayed with 1 per cent calcium hydroxide are fed to larvae
to reduce the occurrence of CPV.
6.4.3. Infectious flacherie
It is the most dangerous and highly contagious disease.
The disease is caused by non-occluded Morator virus belonging to
the family Picornaviridae. The virus is globular and measurers 24-28nm.
Infection takes place perorally. The pathogen preferably infects the goblet
cells. In advanced stage of infection the virus is dispersed in the lumen of
the digestive tract and excreted along with the faeces. The disease never
exhibits the chalky white appearance.
B. Symptoms
The disease shows symptoms like loss of appetite, transparent,
cephalothorax, shrinkage of the body, retarded growth and empty foregut.
These symptoms are followed by vomiting of gastric juice and diarrhoea.
The midgut contains little amount of mulberry lead and full of yellowish
brown fluid. The disease cannot be identified by external features. The his-
tochemical changes of mid-gut tissue can be observed under microscope
(Fig. 6.14).

Fig. 6.14. infections flacherie affected larva
(a) early, (b) late (c,d) midgut of normal and infected

The virus may retain its pahtogenicity in the body of the dead worms
for 2-3 years. Thus the rearing room, appliances and surrounding must be
disinfected using 2% formalin and 0.5% CaOH or bleaching powder. The
other measurers are the same as in grasserie.
6.4.4. Gattine
This disease is also called as the disease of the clear heads.
The diseased caused by a submicroscopic virus to which
Streptochocus bombycia is a secondary invader. At the beginning of the
disease no micro organism is found in the intestine. Later the pathogen
multiplies and causes disease symptoms. The virus alone produces certain
histopathological lesions in the intestinal epithelium. The Streptococcus is
not the principal cause but plays a vital role in the development of gattine.
The infection occurs perorally and through the eggs.
B. Symptoms
The symptoms are clear and prominent when both virus and bacte-
rium occurs in the larva. The larval anterior or cephalic part becomes swol-
len and translucent. The head is clear. Other symptoms are loss of appetite,
ejection of clear ropy liquid from the mouth, diarrhoea.
Maintenance of good sanitary conditions in the rearing room are
necessary. Affected larvae are picked and destroyed.

6.5. FUNGAL DISEASES
These diseases are also called as mycosis, caused by parasitic fungi.
There are two kinds i.e. Muscardine (calcino) and Asopergillosis. The
muscardine disease appears in various forms depending upon the colour of
spores which cover the larval body. They are white, green, yellow, black,
red in colour.
6.5.1. White Muscardine
This disease occurs during rainy or winter season under low tem-
perature and high humidity.
The causal organisma is Beauveria Bassiana (Bal Vuill) belonging
to the family Monliacea. The infection occurs by body contact and rarely
though wounds. The main source of infection are the mummified larvae,
infected seat paper, tray and dead wild lepidopterous larvae. The disease is
highly ontagious.
The fungi shows three stages namely conidium, vegetative myce-
lium and aerial mycelium (Fig 6.15) in the life cycle. The conidia are globular
or oval in shape, colourless and collectively appear chalky white. The conidia
germinates within 8-10 hours after infection under favourable environmental
conditions. The conidia spread throughout the body fluid. The blood be-
comes scanty, blood cells are destroyed and acidity reaches to neutrality. In
advanced stage of infection blood circulation slows down and blood be-
comes pasty and finally larva dies. The conidia germinate in the blood and
penetrate into the adipose tissue, muscles, nervous system, silk gland,
malphigian tubules etc. the conidia on germination gives out germ tube and
secretes chitinase enzyme. This enzyme favours the germ tube to penetrate
into the body wall for further multiplication. The germ tube develops into
vegetative hyphae after invading the blood tissue. After the death of the
silk worms propagation in various tissues is more rapid. The vegetative
hyphae develop round or oval shaped short hyphae at their tips. These de-
tach on their own and elongate to develop into vegetative hyphae. The veg-
etative hyphae bores out of the skin to form aerial hyphae innumerable

conidiophores. The conidiophores produce one or two conidia on their small
branches. Thus the surface of the dead larvae shows white mealy appear-
ance after the formation of the conidia. The conidia are the fresh source to
cause secondary infection.
Fig. 6.15 Development cycle Beauveria bassiana
a) Affected larva
b) Conidia
c) Germination of conidia
d) Formation of cylindrical spores
e) Cylindrical spores
f) A Condiophore with conidia
B. Symptoms
No symptoms are seen during the early stage of infection. As the
disease advances moist specks appear on the skin (Fig. 6.16). the larva
loses appetite and becomes inactive. The body becomes limp, loses elastic-
ity, ceases to move and dies within 3-5 days of infection. The larvae show
diarrhea and vomiting. The dead larval body generally hardens and be-
comes stiff. At this stage the body is pink in colour. The colour is due to
multiplication of secondary bacterium Serratia marcescens.After 2-3 days
of death the body is covered with white wooly aerial hyphae between
intersegemental membrane. Further the whole body is covered with white
powdery conidia except the chitinous parts of the head. The body remains
hard as the fungus secrets of double oxalate crystals of ammonium and
magnesium. The whole body of the dead larva is chalky white and mummi-
fied (Fig. 6.17).

Fig. 6.16. Muscardine affected larva
Fig. 6.17. Mummified Larvae

When the worms are infected before spinning, the larvae spin co-
coons but moths will not emerge. In pupal infection the pupae will not
emerge. In pupal infection the pupae slow down their reaction to outside
stimuli. The thorax shrinks and abdomen is wrinkled. The pupa hardens,
covered with white conidia and dries to one third of its ordinary weight.
These cocoons sound like dried cocoons when shaken. In moths also body
hardens and wings fall of easily.
C. Prevention of Control
Disinfection of rearing room, appliances and surrounding must be
carried using 2 per cent formalin or 5 per cent bleaching powder solution.
During rearing low temperature and high humidity are avoided. The rear-
ing bed must be kept dry to avoid germination of conidia. Infected/diseased
worms are identified and removed before they get mummified. The dis-
eased larvae are put in lime jars or burned along with bed refuse.
Application of formalin chaff at 0.4 per cent during I and II instars
0.5 per cent in III instar, 0.6 per cent in IV instar and 0.8 per cent in V instar
should be followed to control the outbreak and spread of the disease. Fur-
ther Dithane M45 or captan or Reshamkeet Oushadh are used at required
dose (Fig. 6.18).
Fig. 6.18. Application of formalin chaff

Fig. 6.19. Development cycle of Nomuraca riley
a) Attacked larva
b) Conidia
c) Budding of conidia
d) Hyphal bodies
e)Anastomosis of mycelia
f) Condiophore bearing conidia
6.5.2. Green Muscardine
This fungal disease occurs during autumn and winter season.
The disease is caused by Nomuraea riley belonging to family
Moniliaceae. Infection occurs through skin by conidia. The conidia germi-
nate in 15-20 hours after infection under favourable condition. The dead
mummified larva and infected wild lepidopterous insects are the major
source of infection.
The development stages of this pathogen are similar to white
muscardine (Fig. 6.19). The conidia are oval and slightly pointed at one
end. It is light green, single celled, germinate at 22-240
C in 20 hours. The
vegetative mycelium has a germinating tube which elongates to give rise
filamentous mycelia with septae. The mucelia produce colourless tubular
or bean shaped hyphae. Further hyphae from conidiophores, which are wheel
shaped and unbranched. Conidiophores bear a chain of conidia.

B. Symptoms
No symptoms are seen during early period of disease. But at the
later stages dark brown irregular lesions appear on all sides of the body.
Some times the lesions gather to form large spots with clear circumstance.
The laevae show vomiting, diarrhea and finally dies. Then the body slowly
hardens and after two or three days, mycelin appear from spiracles and
intersegmental regions.After 10-15 days the mucelia are covered with fresh
green conidia (Fig. 6.17)
These are similar to white muscardine.
6.5.3. Aspergillosis
Young silkworms are affected by this pathogram when the humid-
ity is high.
The disease is caused by different species of Aspergillus and
Sterigmatocytis belonging to the family Moniliaceae. The important spe-
cies are as follows :-
1. Aspergillus flavus (link)
2. Aspergillus oryzae (Whemer)
3. Aspergillus ochraceus (Wilm)
4. Sterigmatocystis fulva (Saccl)
5. Sterigmatocystis japonica (Aoka)
6. Sterigmatocystis Sp.

Fig. 6.20. Morphology of Aspergillus Sp.
a) Aspergillus flavus b) Aspergillus oryzae
i) Conidiophore i) Conidiophore
ii) Sterigma ii) Phialidae
iii) Conidia iii) Sterigma
iv) Conidia
The developmental stages had conidium, vegetite hyphae and aerial
hyphae (Fig. 6.20). The conidia are spherical, 3-7 m in size which re resis-
tant to environmental conditions and formalin treatment. The conidia ger-
minate at 30-350
C to invade the larval body and develop into vegetative
hyphae. The vegetative hyphae grow at the site of invasion. The conidio-
phores are thick with an expansion at distal end to form globular or oval
structure. It bears one to two rows of radiating sterigmata, on which conidia
are formed.
B. Symptoms
Diseased larvae cease eating become lethargic, show body tension,
lustrousness and finally die. Just before death the head and thorax is ex-
tended outwards and vomiting occurs. The aerial hyphae appear one day
after death and late conidia cover the larval body. Depending on the patho-
gen the colour appears. Depending on the site of fungal penetration, dead
body hardens while other parts turn black and rotten (fig. 6.21)
These are similar to white muscardine. Instead of formalin 4 per
cent pentachlorophenol is used for disinfection.

Fig. 6.21. Aspergillus (a) early (b) late stage

The silkworm diseases are caused by protozoans, bacteria, virus
and fungal pathogens. Among protozoan diseases pebrine is a
chronic and dangerious disease caused by Nosema bombycis. The
disease is transmitted through egg from one generation to the other.
Dead worms, infected worms and bed form major source of infec-
tion.
The disease shows symptoms in all life stages of silkworm. Eggs
are laid in lumps with less adhesive.
Larvae become sluggish, show retarded growth, loose appetite, moult
irregularly, show pepper like spots on the skin.
The infected pupae are flabby and swollen with lusterless. Moths
show clubbed wings, discolouration of scales, falling of scales, de-
lay in emergence.
The pebrine spores are identified by mother moth examination un-
der microscope with 600 magnification.
Perfect surface sterilization, production of healthy eggs prevents
the disease.
Bacterial diseases (Flacherie) are septicemia, bacterial diseases of
digestive tract and sotto.
In septicemia the bacteria multiply in the haemolymph of larva,
pupa, adult.
The Body wall oozes fluid when punctured.
The transparent disease is caused by Streptococcus sp. Poor nour-
ishment and adverse environmental conditions favours the diseases.
Generally the symptoms resemble septicemia.
Sotto is caused by Bacillus thuringinesis which has three stages.
The pathogen spore produces delta endotoxin. Infection is through
wounds or preoral.
SUMMARY

v The infected larvae lose appetite, show convulsions sluggishness,
lack of skin tension, shrinkage of the body, tremors etc.
v Viral diseases of silkworms cause 70 per cent damage to sericulture
industry.
v The nuclear polyhedrosis is caused by Borrelina bombycis. The vi-
rus multiplies and forms polyhedra in the nucleus of tracheal epi-
thelial cells, blood cells. Infection is by feeding polyhedra along
with mulberry leaf.
v The larval body becomes milky white with intersegmental swell-
ing. the skin ruptures easily liberating the liquefied body contents.
v Cytoplasmic polyhedrosis is caused by Smithia virus. The polyhe-
dra are formed in goblet and regenerative cells. Infection is though
polyhedra contaminated mulberry leaf.
v Infections flacherie is caused by Morator virus which infects by
entering preorally.
v Gattine is caused by submicroscopic virus which produces certain
histopathological lesions in the intestinal epithelium.
v Muscardine is caused by a fungal pathogen. It appears in various
forms depending upon the colour of spores which cover the larval
body. The white muscardine is caused by Beauveria bassiana while
green muscardine is caused by Nomuraea rileyi.
v Infected seat paper, dead wild larvae, mummified larvae are main
source of infection.
v The larva loses appetite and becomes inactive, body becomes limp,
loses elasticity, ceases to move and die.
v The dead larvae hardens and becomes stiff. The dead larvae devel-
ops white, wooly aerial hyphae between intersegmental membrane.
v The complete body is covered with white or green powdery
conidia. Disinfection of rearing room, appliances must be carried
using formalin.
v Aspergillosis is caused by different species of Aspergillus and
Sterigmatocytis.

I. Short Questions
1. How do you detect pebrine in silkworm ?
2. What symptoms are seen in pebrine affected larvae ?
3. What are the features of Sotto disease ?
4. How do you identify muscardine ?
5. What are the symptoms of flacherie ?
6. What is the causative organism of pebrine ?
7. Mention silkworm diseases ?
8. Draw the diagram of Pebrine spore ?
9. What is the causal agent of Septicemia ?
10. Mention bacterial diseases ?
11. Mention viral diseases ?
12. What is causal agent of CPV, NPV ?
13. What is the other name of gattine disease ?
14. Mention fungal diseases ?
II. Essay Questions.
1. Explain the disease caused by Nosema ?
2. Detail about muscardine (white) disease ?
3. Explain about septicemia disease ?
4. Detail about Sotto disease ?
5. Explain NPV disease. Add a note on its control ?
6. How do you identify pebrine disease ?
7. Write about gattine disease ?
8. What are the symptoms of fungal disease ?
9. Add a note on symptoms of pebrine disease ?
10. Write short notes :
a) CPV b) Aspergillosis
a) Gattine b) Septicemia
QUESTIONS

7
SILKWORM PESTS
7.1. INTRODUCTION
There are different microorganisms, which cause diseases beside
serious pests like uzy and dermisted beetle attack silkworms and stored
pests affecting the crop yield and quality. The symptoms of different dis-
eases vary. Some have specific symptoms and others have common symp-
toms, such as fast or slow larval growth, late mouling nonmoulting, irregu-
lar growth, poor appetite, unusal behaviour abnormal spots ont the skin,
changes in body colour, defects in intersegmental membranes, abnormal
saliva or excreta, unusually soft or hard skin and which can be observed
with the naked eye. These feature facilitate the rearer to identify the dis-
ease.
Pests of silkworm can be seen with naked eye. The larval stage are
affected by uzy fly while dermisted beetle is fond of eating pupae. Thus it
requires proper preventive measures rather than its control.
Keeping in view of all the above facts, healthy silkworm strains are
selected and properly reared by adopting modern methods to keep away the
incidence of diseases. It is also necessary to disinfect the rearing chamber,
equipment etc., to kill pathogenic organisms.
7.2. Major Pests
7.2.1. Uzy fly
The parasitoid insect belongs to order Diptera and family Tachinidae.
This pest incidence is very high in tropical contries like Bangladesh, China,
India, Thailand and Vietnam. Tricholyga bombycis is a major pest of silk-
worms.

SILKWORM PESTS 115
7.1.1.1. Life Cycle
The life cycle has four stages i.e., adult, egg, maggot and pupa (Fig.
7.1.).
A. Adult
It is blackish gray in colour and distinguishable into head, thorax
and abdomen. The head is triangular in shape with conical abdomen. Tho-
rax has four longitudinal black bands on the dorsal side, while the first
abdominal segment is black and rest grayish yellow. The life span of adults
varies with sex and season. Males survive for about 10-18 days. And fe-
males live 2-3 days longer than males. Survival period is long during sum-
mer.
Sexual dimorphism is very clear in uzy fly. Males are longer (12
mm) than females (10mm). Male has external genitalia covered with brown-
ish orange hairs on the ventral side of the abdominal tip. The bristles on the
lateral region of abdomen are more dense in male, while they are restricted
to last two segments in females. The width of the frons of the male fly is
narrower than that of female.
Generally males strike the resting and walking females. Mating strike
is followed by agitated state of the female before successful genetal con-
tact. This premating period prolongs for about 4-6 hours.
Fig. 7.1. Uzy life stages

The polygamous adults mate 1-2 times after emergence and 3-7
times within 24 hours in the entire life. Mating occurs during early morn-
ing or late in the evening, with a duration ranging from half an hour to two
and half hours. But it requires a minimum of one hour mating for full fe-
cundity and maximum hatchability.
Female fly starts egg laying 44-45 hours after emergence. The fly
prefers to lay egg on late instar (3rd
instar onwards) because of relative area
of the silkworm body.After repeated survey the fly settles down on the host
for ovipostion. Under normal condition 1-2 eggs are laid per larva. The
eggs are laid at intersegmental area.
A single female lays about 300-1000 eggs over a period of above 9-
25 days. Initially few eggs are laid which gradually increases to reach the
peak between fourth and seventh day after emergence. But egg laying de-
creases with advancing age. Female fly lays eggs throughout its life.
B. EGG
The eggs are creamy white measuring 0.45-0.56 mm in length and
0.25-0.30 mm in width with along shape. Depending on the environmental
conditions the eggs hatch in about 2-5 days after laying. The newly hatched
maggot penetrates into the silkworm body.
C. MAGGOT
The maggot hatches out through operculum of egg shell which gen-
erally faces the silkworm body. The maggot penetrates into the silkworm
which is surrounded by a sheath formed by granulocytes and proliferating
tissue at the site of the wound. With the growth of maggot the size of the
sheath increase and becomes thick and black which finally seen as a black
lesion or scar on the silkworm body. This is a good identification of uzy
infestation.
The first and second instar maggots are yellowish white in colour
measuring 0.7-1.5 mm and 2.75 mm width and length respectively. The
third instar maggots are creramy white measuring 1.3-1.6 cm in length.
Maggots have eleven body segments and pass through three instars. The
first two instars develop just below the skin but final instar maggots move
into the body cavity and grows in size. After a lapse of 5-8 days the mature
maggot escapes by piercing the host integument by its prothoracic hooks.

SILKWORM PESTS 117
The maggot feeds on the body tissues of silkworm and the host dies
by the time maggot escapes.
C. PUPA
Maggots pupate in about 10-20 hours in the darker area in and around
the silkworm rearing house like rearing beds, crevices, corners, below ant
wells and rearing stands or in the superficial soil. The body becomes mo-
tionless and shrinks before pupation. Pupae are oblong in shape, reddish
brown to dark reddish brown in colour, with elevean segments and mea-
sures 0.9-1.2 cm in length and 0.4-0.6 cm in width. It takes 10-12 days to
metamorphose into adult which emerges out.
7.2.1.2. Damages and Symptoms
Infested larvae upto early fifth instar die before spinning. Of the
larvae are attacked in fifth instar the maggot comes out by piercing the
cocoon.
Uzy infected worms are identified by black scar at intersegmental
region where the maggot penetrates into the silkworm body. Minute creamy
white eggs are observed on the larvae at the initial stage of infestation.
Maggot pierced cocoons are unfit for reeling (Fig. 7.2).
7.2.1.3. Prevention and Control
Good sanitary and hygienic conditions in and around rearing room
are important. The holes and crevices in the rearing room are to be closed
before rearing activity. Early spinning cocoons which are generally uzy
infested, and are to be carefully separated from normal cocoons. These
cocoons are stifled to kill the inside maggot (Uzi).
A physical barrier is created in the rearing room to prevent uzi en-
try. Fine wire mesh barrier in the doors and windows or mosquito net cur-
tain around the rearing stand will solve the problem. Dusting of levigated
china clay on the body of silkworm during mounting prevents oviposition
by uzi.

Fig. 7.2. Uzy Infection

SILKWORM PESTS 119
In chemical control, uzicied containing one per cent of Benozoic
acid is recommended at the dose of 7.8 m.sq.ft. It is effective when applied
within 48 hours of egg laying. Control of uzi fly is effective against use of
2.5% difulubenzuron.
Control of uzi fly through biological means (hyperprasitoids) is better. A
number of parsitoids of uzi fly pest of silkworm have been identified which
are as follows. They are Trichopria sp., Nesolynx thymus, Exoristobeia
philippinensis, Dirhimus himalayanus, Brachymeria lugubris,
Spilomucrus Karnatakensis, Splangia cameroni and Pachycrepoideus
vindimmae.
7.2.2. Dermestid Beetle
Among pests coleopteran insects cause much damage to stored co-
coons. These insects are harmful to silkworm directly sometimes indirectly.
Most of the damage is done by the larvae when cocoons are stifled and
stored for a long time. The pest larvae bores the holes to the cocoons and
the pupae are eaten. Besides this, they also damage animal and plant prod-
ucts including leather, furs, dried fish, carpet, woolen and silk materials.
These beetles belong to family Dermestidae.
7.2.2.1. Life Cycle (Dermested Cadverinus)
The adult insect is oval-elongate and dark brown in colour. It mea-
sures about 1 cm in body length. The adult lives on animal matter for one
year after oviposition. Generally the pest passes the winter in the adult
stage, and begins mating and starts egg laying in May. After mating the
female beetel moves around in dark places in the cocoon storage room and
deposits eggs in the crevises. Each adult lays 50-400 eggs. The eggs hatch
in a week. The grubs are spinkle shaped, reddish brown in colour. The
insect prefers to be in dark places. Grub moult 5-7 times in about 1-2 months
and attains a length of about 1.5 cm. the body of the grub is covered with
hair. Then grub becomes pupa. The adult after emergence mates and lays
eggs which develop to become the adults of second generation (Fig. 7.3).

Although the insect generally passes the winter in the adult stage,
since the time of metamorphosis is not fixed both the larval and pupal
stages may be encountered in winter. The other dermisted beetles that are
important from sericulture point of view are as follows:
1. Dermestes valpinus (Fab)
2. Dermestes vorax (Motschulsky)
3. Dermestes frishehi
4. Dermestes tessolatocollis
5. Dermestes coarctatus
6. Trogoderma versicolor
7. Anthrenus verbasi L.
8. Anthrenus pipinellae Fab.
9. Attagenus piceus (Oliver)
10. Attagenus japonious (Reitter)
7.2.2.2. Damage, Symptoms, Prevention, Control
The larva and adults are attracted by the smell of stifled cocoons
and the dried pupa inside. They bore into the cocoons and eat the dried.
Pupae and sometimes eggs. Damaged cocoons are unfit for reeling. Rarely
the young larvae attack living silkworms. The pests occur throughout the
year causing damage to stored and stifled cocoons.They also damage pierced
and melted cocoons which are stored in the grainage building. Presence of
cocoon pierced at several places and the egg laying silkworm adults in the
grainages damaged mostly on the abdominal parts are indications of at-
tacks by dermisted beetles.
Fig. 7.3. Dermisted life stages

The rearing house and cocoon storage rooms should be cleaned pe-
riodically. Storage of rejected cocoons for long period should be avoided,
wooden equipment are to be dipped in 0.2% malathion for 2-3 minutes.
After 10 days the trays should be washed in water and sun dried for 2-3
days before re-use. Passing of hot air (50-600
C) and maintenance of low
humidity (30%) also help to kill the beetles. Fumigation with methyl bro-
mide 0.5 gr. Per 3m2
for three days kills all the stages of beetle.
7.3. Minot Pests
Besides major pests there are many minor pests than cause damage
to silkworms as well as to cocoons and increase cost of production and
crop loses.
7.3.1. Mite (Pediculoides ventricosus)
This non insect pest belongs to the orderAcarina and classArachind.
This mite is encountered at the time of re-thaching of the roof of the silk-
worm rearing house or brought into the rearing room along with building
material such as straw, wood or bamboo. The female mite attacks all the
stages of silkworm except eggs, causing death.
Both the sexes are in different shape. The adult fully grown female
has a swollen around abdomen 30 times the normal ordinary size to attain
spindle shape. Males are oval shaped. Head is triangular and thorax-abdo-
men carry four pairs of legs each having small claws. This pest is ovovi-
viparous. I female the young acarids hatch out from the eggs and pass out
in the form of adult like small acarid. Each adult produces about 100-150
young ones. The newly born mite is about 0.2 mm in length with light
yellow colour body. Males are produced first than females. Each male after
matching with some females dies in about a day. Female mite with large
number of eggs attains spherical shape as posterior half of the body be-
comes enlarged. Fertilized female gets attached to the suitable host with its
claws and suckers.Young larvae and pupae of silkworm are preferred hosts.
The mite passes through 17 generations in a year. Each generation time
ranges between 7-18 days (Fig. 7.4).
SILKWORM PESTS 121

The larvae, pupa and adult silkworm are attacked by this pest. The
body surface of a silkworm stuck with this mite, develops a few black
specks. The purpose of attachment between the host and pest is to obtain
nutrition. Further, the pest animal saliva contains toxin which ultimately
kills the host. The infested silkworms loses appetite, becomes inactive and
has difficulty in excreting. It takes time to pass the excreta and frequently
the excreta are attached bead like to the anus. In severe infestation, silk-
worms vomit yellowish green fluid and excretes black fluid from the anus.
Irregular and decreased pulsation of the dorsal vessel occurs. The skin sur-
face of the attached host bears several rough and uneven black sports. Worms
attacked during moult fail to pass the moult and die in a day or two. In-
fested pupae develop lesions, the body is blacken and they fail to moult
into adult. In acute attack, silkworms die in as few hours and starts putrifying.
Young silkworms do not putrify rapidly.
On identifying acarid attack the rearing room and trays should be
replaced. All the appliances should be disinfected with steam. Straw (Cot-
ton, Rice) should be kept away from rearing room and appliances.
7.3.2. Ants
Ants attack silkworms in the rearing trays, can be prevented by plac-
ing the legs of the rearing stands in ant wells. Dusting of gamzxine of
pouring of little kerosene around the legs of rearing stand and chandrika
prevents ant crawling.
Fig. 7.4. Pediculoides

7.3.2. Nematodes
The nematode Hexamermis Microamphidis is found in silkworms
of late autumn rearing. This worm attacks the young silkworms and pen-
etrates into the body. The head of the affected silkworm becomes transpar-
ent and the body turns milk white.
7.3.3. Lizards
These reptiles re seen frequently on the rearing houses. These pests
cause serious damage to the rearing by swallowing young silkworms.
7.3.4. Rats and Squirrels
These pests eat silkworms avoiding on silk gland and the pupa after
opening the cocoons. Thus entry of these animals is to be prevented by
arranging suitable wire mesh for doors, windows and ventilators.
7.3.5. Birds
Crows, sparrows pick up the silkworms when the mountages are
kept our doors at the time of spinning. The damage caused by these birds
can be avoided by indoor rearing.
The parasitoid pest (uzifly) has four life stages i.e. adult, egg, mag-
got and pupa. The adult shows sexual dimorphism.
The fly is blackish gray with head, thorax and abdomen. It lives for
about 20 days.
Female fly lays about 300-1000 eggs at the intersegmental region
of late age worms.
SUMMARY
SILKWORM PESTS 123

The site uzy maggot entry becomes black. Maggot passes three in-
stars and escapes out side by killing the larvae. Pupae are formed in
dark areas which metamorphos into adult in 10-12 days. Infected
larvae die before spinning.
The pierced cocoons, melted cocoons are unit for reeling.
The uzi fly can be controlled by a physical barrier, uzicide and
through biological control.
Dermested beetle (Coleopptera insect) causes much damage to stored
stifled cocoons. Its life stages are egg, grub, pupa and adult.
The adult and grub causes damage to sericulture industry.
Grub moults 5-7 times in 1-2 months then undergoes pupation and
metamorphose into adult.
The grubs and adults are attacked by the smell of stifled cocoons
and make them unfit for reeling.
Maintenance of good and bygienic conditions helps to reduce the
attack.
There are some minor pests such as mites, ants, nematodes, lizards,
birds, rats and squirrels which contribute to damage worms and
cocoons.
Among all mites cause mush damage.
All these can be controlled by adopting simple preventive precau-
tionary measure during rearing activity.

SUMMARY
I. Short Questions
1. Mention pests of silkworms.
2. How do you identify uzy fly ?
3. What are the symptoms of uzy infection ?
4. Mention minor pests of silkworms.
5. How do you control uzy fly ?
6. How do you prevent minor pests ?
II. Essay Questions
1. Detail about the damage caused by uzy fly.
2. Explain the life cycle of dermisted beetle.
3. Write about minor pests and add a note on control.
4. Write short notes
a) Symptoms of uzy attack b) Minor pests
SILKWORM PESTS 125

8
ECONOMICS
8.1. INTRODUCTION
The economics of any holding depends on various activities. Seri-
culture is not an exception. No doubt all the aspects right from moriculture
to silk reeling have very good commercial value. Silkworm rearing is to be
conducted systematically. All the aspect directly or indirectly influence the
rearing and reflect on cocoons production. On the other other hand cocoons
quality and quantity also depends on various activities of rearing. In other
words the crop economics is influenced by the rearing activities. The crop
expenses are much less for disease control and labour. However a rearer
should know the economics of silkworm rearing and the factos that hamper
the cocoons production.
The by products of silkworm rearing can be used for various pur-
poses. Some of them (excreta) are very good source for production of im-
portant chemicals used in industries like pharmaceuties, chemical indus-
tries, fertilizers. In this chapter economics and by products of silkworm
rearing are discussed.
Sericulture is an agro-based industry which requires a proper plan-
ning to ensure successful crop results. The rearer should have an idea about
the crop which he is going to start. Like other crops, sericulture has differ-
ent aspects i.e. mulberry cultivation, grainages, silkworm rearing and reel-
ing. And it is necessary for a beginner to know about the economics of
sericulture industry. There4 by he proceeds further with care and confi-
dence. Further he must have an idea regarding various operations involved
in a particular branch of sericulture. All the information regarding various
operations and aspects are noted in different specific records from time to
time for getting good results. Silkworm rearing also requires certain records
to be maintained by the rearer as a guidance.

ECONOMICS 127
8.2. ECONOMICS OF REARING 300 DFLS OR ONE ACRE
From economics point of view the improved techniques of rearing
are more important, for achieving good crop results. The profits are nearly
50 per cent more than normal rearing processes. The new techniques of
rearing are to be followed right from the selection and cultivation of mul-
berry. Hybrid variety of mulberry i.e. M5 yields more quantity and quality
of leaf/acre when compared to local varieties. Further by adopting various
latest cultural and irrigation processes the yield can be still increased.
Selection of proper seed for rearing is more important as diseased
layings yield poor crop and low quality of cocoons. For this purpose hybrid
multivoltine and hybrid bivoltine races are selected for rearing purpose.
The third and final important part of sericulture is rearing. The rearing of
worms should be conducted in a methodical way. Thereby the no. of co-
coons per crop per acre increases when compared to normal process of
rearing. The improved techniques of rearing includes selection of rearing
house, provision of proper environmental conditions, quality of leaf to feed
the worms and leaf preservation methods. Depending on the growth of the
worms they are to be properly spaced. Further the worms are given quality
lead depending on the age of worms. Care should be taken during moult-
ing, feeding, bed cleaning, mounting, harvesting. During the process of
rearing disinfection of rearing room is advisable so as to prevent incidence
of the diseases and also to maintain proper hygienic conditions.
By adopting chawki method of rearing and late age rearing sepa-
rately, helps the farmer to maintain proper environmental conditions. Fur-
ther the equipment also differs in both rearing. It is also advised to rear
chawki worm in co-operative rearing centers. This enables to reduce the
expenditure and also to ensure proper growth of the worms under the su-
pervision of technicians. Maintenance of optimum environmental condi-
tions during spinning and mounting also increases the quality of cocoons.
Thus by adopting the above mentioned new techniques more profits can be
achieved instead of following old traditional methods of rearing.

Sl.
No
Equipments
Required
No.
Cost per
item Rs.
Total cost
Rs.
Utility
(Yrs)
Value Per
Yr. Rs.
Building (rearing house)
plinth area 1053 sq. ft. cost
of construction
@ Rs. 125/- per sq. ft.
Rearing stands
Rearing trays
Round bamboo trays
Leaf chopping boards
Chopping knives
Feeding stands
Leaf chamber
Sprayer
Hygrometer
Foam pads
Chandrikas (bamboo)
Cleaning nets
1
2
3
4
5
6
7
8
9
10
11
12
4
30
100
2
2
4
1
1
1
1kg
60
300
500/-
80/-
25/-
150/-
40/-
75/-
300/-
750/-
250/-
150/-
50/-
5/-
2,000/-
2,400/-
2,500/-
300/-
80/-
300/-
300/-
750/-
250/-
150/-
3,000/-
1,500/-
10
10
3
10
3
10
10
10
10
4
3
3
200/-
240/-
840/-
30/-
27/-
30/-
30/-
75/-
25/-
38/-
1,000/-
500/-
TOTAL 13,530/- 3,035/-
13
1,31,625/- 50 2,633/-
Table. 8.1 Investment on equipment for rearing 325 DFL’s in one acre
of mulberry under Irrigated conditions (approximately).
The silkworm rearing capacity and crop pattern mainly depends
upon the leaf yield. The full impact of the yield and economics will be seen
from third year onwards only. During the first year, two crops can be taken
and the leaf yield and rearing capacity is limited to about 325 dfls under
irrigated condition.

from second year onwards the leaf yield increases to 14,000 kg per acre
with a rearing capacity of around 1625 dfls (five crops in a year). From
second year onwards the net profit per acre is about Rs. 25,660.50 per five
crops.
Table. 8.2 Expenditure on rearing 325 dfls (approximate)
Sl.No Item Total Cost
Rs. Ps.
Cost of dfls @ 250/- per 100 dfls so 1625 dfls cost
Cost of labour wages
Young age 14 days, 3 men/day= 42 days
Late age 14 days, 5 men/day=70 days
Spinning and harvesting
2 days, 8 men/day = 16 days
Total = 128 days
Labour charges @ 20/- = 128 X 20
Misc ie. paraffin paper, formalin, news paper,
transport etc.,
Non-recurring expenditure on rearing
equipments and moriculture equipments
Building value
Leaf production (14,000 kg per year)
@ 0.78ps. per kg.
1.
2.
3.
4.
5.
6.
4,062=50
2,560=00
1,000=00
4,316=00
2,633=00
10,956=00
GRAND TOTAL 25,527=50
Cost of production of cocoon is Rs. 44.88ps./kg green cocoons.
ECONOMICS 129

Table. 8.3 Net Profits from one acre of mulberry/year.
Sl.No Item Profits
Rs. Ps.
Returns through sale of cocoons of 568.75 kg.
@Rs. 90/- per kg. @ 35 kg cocoons for 100 dfls.
Expenditure per one acre per year
1.
2.
51,187=50
(-) 25,527=50
GRAND TOTAL 25,660=50
NOTE : Above data may change from time to time according to cocoon
market, grainage etc.
8.3. BY PRODUCTS
Sericulture is an agro based industry which includes various as-
pects such as mulberry cultivation, grainages, silkworm rearing and reel-
ing. These different aspects are very much associated with each other as
one depends on the other. One has to be a successful sericulturist, he must
have a planned approach. The most important factor of the planning would
be adoption of new technology to get more profits. Further a proper plan-
ning with an integrated approach where sericulture can be combined with
pisciculture, dairying sheep/ goat rearing and poultry farming. The project
could be undertaken taking account of waste products or by-products in the
sericulture and their utilization.
Like other crops sericulture also leaves some by-products at every
level, and these can be utilized in many ways. We can proudly say that
“Nothing is waste in Sericulture”. Further this aspect also gives lot of scope
for self employment where they are involved in collecting the by-products
and transporting to the particular person/industry.
The sources of by-products are mulberry garden, grainage silkworm
rearing and reeling.
The mulberry crop has to be well manured. The manuring includes
cattle manure, manure of sheep/goat and silkworm faeces. It may be sug-
gested that an effective, modified recycling procedure would be to dump
silkworm faeces into fish ponds, where it can become the source of nutri-
tion as a fish food.

Silkworm litter can be used a fertilizer as it contains more amounts
of nitrogen. It is also used in bio-gas production. Excess of harvested leaves
(accounting for 10-20% of harves), unfed leaves (20-30% of leaves fur-
nished at each feed), larval litter (60% of ingested food), and exuvia of the
moulted larvae are the major wastes generated in this activity. They are
collected daily during bed cleaning. A part from these, rejects, or worms
rejected because they are weak, diseased or unhealthy, and dead larvae also
constitute wastes. The following uses have been found for them.
8.3.1. Uses of leaf and litter as compost
The amount of nitrogen, phosphorus and potassium present in the
left-over mulberry leaf is 3.1, 0.5 and 1.5% respectively and that present in
the silkworm litter is 1.4,0.4 and 0.8% respectively. These can be added to
the soil if they are converted into compost.
For preparing compost from the mixed sericulture farm wastes, they
are collected in pits of convenient size (4.5 X 1.5 X 1m3
). Each day’s col-
lection of silkworm litter, mulberry left-over leaves, weeds (grasses etc) are
spread in a thin layer.Amixture of fresh cowdung solution (4-5 kg cowdung
in 100 liters of water) or biogas slurry, ashes (140-170g) and water (18-22
liters) is sprinkled on the layer to make it compact and 150-200 gm lime
powder is also added to the mixture to create a buffer effect. At the end of
the rearing the left-over leaves in the garden along with the young mulberry
twigs are also added to the pit. Some amount of chemical fertilizer, prefer-
ably, single super phosphate of lime is added to enrich the nutrient value of
the compost. When the pit is filled, it is plastered with a 25 cm layer of a
mixture of mug and cowdung. This prevents flies from collecting on the
garbage and creating nuisance.Ashed of asbestcs or thatched roof prevents
the pit from being soaked with rainwater. Compost can be dug from it after
three or four months.
By this method, about 5-6 Mt of well-decomposed and nutritionally
rich compost with 30% moisture will be available from one acre of mul-
berry farm. The resulting compost contains 1.6%N, 0.7% P and 0.3% K, in
addition to various micronutrients. Use of compost as fertilizer enriches,
maintains and restores the health of low-humus-containing tropical soil. It
not only increases the productivity of soil and improves yield, but also checks
soil erosion by enriching the binding properties of the soil by improving
soil structure, drainage and its base-exchange capacity. It destroys harmful
human pathogens that may grow on the garbage and also helps to prevent
environmental pollution.
ECONOMICS 131

8.3.2. Use of larva as Animal feed
Rejects and dead larvae can be used as poultry feed. Chicks fed on
them lay bigger and more number of eggs because the silkworm contains
high protein content. Cast larval skin is also good food for poultry.
8.3.3. Use of silk gland as suturing material
Mature silk glands from dead worms can be used as the source of
guts which are used for surgical suturing. This can be done by treating the
silk glands with acetic acid and then drawing them into fine filament.
8.3.4.a. Uses of litter as Biogas
Silkworm litter can be effectively used as raw material in the biogas
plant along with cowdung to produce fuel. It is better to use litter for fuel
production than for fertilizer as it may contain spores or other resistant
stages which may remain in the soil and maybe transferred to the next gen-
eration.
The quantity of cattle manure available with small and marginal
farmers may not be sufficient to feed a small 2m3
biogas plant. Silkworm
larval litter with a better biogas yield (96.20% more than cowdung) can be
used as a supplement to cowdung in the biogas plant. Experiments have
revealed that silkworm-larval-litter-incorporated treatment increases the
biogas generation (from 56.97 to 96.20%). The quantity of gas produced
per gram of total solid destroyed was also high in cowdung0silkworm litter
incorporated treatment. The manorial value of the biodigested slurry was
also increased due to its incorporation with the litter. Nitrogen, phosphorus
and potassium were all high in the slurry obtained by using dung with litter
than dung alone.
The reduction microorganisms pathogenic to both mulberry and silk-
worm are alos possible in the bioidigester, since the environment in the
digester is not conductive to the survival of these pathogens. This leads to a
break in the perpetuation of pathogens and reduces the loss in cocoon crops
due to diseases.
8.3.4.b. Pharmaceutical Industry
In China silkworm litter was used as manure, feed for fish during
1950. pharmaceutical and perfumery compounds are produced from silk-
worm litter in China. In 1970 paste chlorophyll, copper chlorophyllin sodium
was produced from silkworm litter. In 1975 phytol, kerotine, triactinal, pectin
were produced to utilize them in food, chemical, pharmaceutical, cosmetic
industries. Being the largest producer, of raw silk in the world, it accumu-
lates large quantities of silkworm excreta (4,00,000 tons a year) and
converts it into raw material for synthesizing many new product of which

chlorophyll (C55
H72
MgN4
O5
RCH3
) is worth mentioning because it is in de-
mand internationally for pharmaceutical and food processing industries.
Food processing industries. Chlorophyll extracted from pine needless and
forage grass are used as a colouring matter of chlorophyll soaps, food, waxes
and toothpastes. It is also used as a deodorant, healing agent and as medi-
cine for stopping bleeding of teeth and gums during dental and gum dis-
eases. It is estimated that 20 tons of silkworm excrement can produce one
ton of chlophyll or 30 kg of sodium iron chlorophyll and that too with less
expenditure than the conventional process of manufacturing it from dried
alfalafa leaves. They have also developed a technique for producing fruc-
tose form silkworm litter.
The Zhejiang Akademy ot Trational Chinese Medicine has devel-
oped ganzuebao, a medicine for hepatitis and leukemia, made from chloro-
phyll extracted from silkworm excrement. According to the chief of the
research group that studied the use of silkworm excrement, this medicine
has a efficiency rate of 95.6% for cancer patients suffering from loss of
white blood cells caused by chemotherapy and radiotherapy.
Table 8.4. Other by products and their uses.
Sl.No Product Uses
Paste chlorophyll
Copper chlorophillin sodium
Phytol
Triactinol
Kerotine
Pectin
Chemical industry
Pharamceutical industry (fo Human
stomach, liver, pancreas, cronic renal
diseases); for wine, fruit concentrate
preparation; Toothpaste, shampoo
preparation.
To produce vitamin (K,A)
As growth regulators in rice, wheat,
maize, groundnut, vegetables
To produce K vitamin, medicine for
stomach, lung disease. To prevent
cancer to these organs.
For preparing Jam, fruit juice
concentrates, ice creams, medicines to
control pressure and cholesterol
1.
2.
3.
4.
5.
6.
ECONOMICS 133

8.3.5. Pierced cocoons
Pierced cocoons produced in rearing are categorized as grade I waste.
These cocoons and cut-open cocoons form the raw material for hand-spin-
ning industry to form silks like ghicha and katia which are used for produc-
ing fabrics like gent’s chaddar, lady’s scarves, curtains, table cloth and caps.
It is also used for producing spun silk in mills. These are also used for
garland and other decorative items.
8.3.6. Uses of Waste Moths
The moths unused for seed purposes, dead months, and the dis-
carded eggs are generally dumped in pits and allowed to form compost
without any commercial motive. But as some of these discarded moths and
eggs are pebrinished, they may spread pebrine to the seed cocoons reared
unless special care is taken to burn them.
The silkmoths, which are discarded after emergence or after mat-
ing, are now used to brew medicinal wines in accordance with ancient Chi-
nese prescriptions. The best known is a male silkworm moth wine pro-
duced by Shaanxi Sericultural Technology Station. According to Wang
Xinhua, a senior agronomist, the liquid can be used to treat impotence,
abnormal menstruation and menopausal symptoms.
8.4. RECORDS AND USES
Maintenance of records helps the farmer to understand and act ac-
cordingly. It helps in money and man-power management.
8.4.1. Dairy
It is a useful record of rearing. It records the operations conducted,
equipment used, labour-employed and money received and paid. Weather
conditions and important events to be undertaken in future are also noted
in the diary.
8.4.2. Cash Register
It is also maintained daily by recording the details of cash received
and cash paid.

8.4.3. Egg Purchase Register
It is a record for entering the purchase of layings in a particular
rearing, season and year. Nomenclature of the eggs such as race, voltinism,
breed, etc., are noted for future record purpose. Further names and places
of available4 grainages are also entered in the register.
8.4.4. Feed Register
Is is a record for entering all the feeds. The silkworm leaf eating
capacity increase from fitst instar to last instar. So depending on their di-
gestibility they are to be given adequate amount of mulberry Leaf. The
records should contain day wise and feed wise record for every rearing.
This also helps to know about the leaf utilised in a particular rearing.
8.4.5. Cocoon Production Register
It contains the record of cocoons produced in each rearing i.e. no of
kg/crop or rearing/season/ it also contains the incidence of diseases in a
particular crop, nature of damage caused by the pathogen and details of
economics of rearing.
Further it contains rate of cocoons per kg of each rearing and name
of the market where it is sold.
8.4.6. Wage Register
It is a register for the permanent labour force employed and the
casual layout hired and their wages, attendance.
8.4.7. General Register
It is a record of miscellaneous items of expenditure such as land
revenue, water rates, replacement of grainage implements and machines,
tools, disinfactants etc.
8.4.8. Inventory
It is property record. It shows the number and value of each item
such as land, building, water supply, livestock, equipment, machinery, cash
in hand and in the bank and the amount to be paid or received.
ECONOMICS 135

SUMMARY
Improved techniques of rearing are more important, for good crop
results.
All the aspects of silkworm rearing are carried with lot of care.
Leaf yield increase from second year onwards with a rearing
capacity of 1625 dfls (Five crops per year)
The byproducts of sericulture are used for various industrial
purposes.
Excess leaf, litter is used for compost preparation containing
1.6%N, 0.7%, P and 0.3%K besides many micronutrients.
Dead larvae are used as animal feed. Silk glands of dead larvae are
used for preparing suturing material.
Silkworm litter can also be used in biogas production.
In China silkworm litter is used in large scale for extracting paste
chlorophyll, copper chlorophyllin sodium, pectin, kerotine, phytol,
triactinol. All these are used in pharmaceutical, food, chemical and
cosmotic industries.
Pierced cocoons are used for hand spinning to get silk like ghicha,
katia.
Waste moths are used for compost, to treat impotence, abnormal
menstruation and menopausal symptoms.
Maintenance of records helps the rearer to carry on various activi-
ties in time.
Diary is for recording daily operations performed in the rearing.
Egg details are noted in egg purchase register.
Feeding schedules are entered in fedd register.
Crop produce are noted in cocoon production register.
Further wage register, inventory, general registers are also main-
tained.

I. SHORT QUESTIONS
1. Mention the factors that influence economics of rearing
2. What are the reasons for poor cocoons crop ?
3. Mention by products of silkworm rearing.
4. What are the uses of waste mulberry leaf ?
5. Mention the chemicals extracted from silkworm litter.
6. What are the uses of silk gland
7. Mention the uses of pectin
8. What are the uses of waste moth ?
9. What are the uses of diary ?
10. Mention any four records used in rearing house.
11. What do you entire in general registger ?
II ESSAY QUESTIONS
1. Detail about the economics of silkworm rearing
2. Explain the uses of silkworm litter
3. Brief about by products of rearing and their uses.
4. Write about rearing records.
QUESTIONS
ECONOMICS 137

1. Silk Worm Rearing, Volume-2-15/2, FAQ of United Nations,
Rome, 1987.
2. Appropriate Sericulture Techniques,Manjeet S.Jolly, CSRTI,
Mysore, 1987.
3. Hand Book of practical sericulture, Ullal & Narsimhanna, CSB,
Bangalore, 1981.
4. Hand Book of Silkworm Rearing, Tazima, Agriculture Techni-
cal Manual-1, Fuji Publishing Co. Ltd., Japan, 1992
5. Techniques of Silkworm Rearing in the Tropic, ESCAP, United
Nations, New York, 1993.
6. New Illustrated Sericulture Reader, CSB, Bangalore, 1997
7. New Technology of Silkworm Rearing, S. Krishnaswamy,
CSRTI, Mysore.
8. An Introduction to Sericulture, Ganga & Sulochana Chetty,
Oxford & IBH Publishing Co. (P) Ltd., New Delhi, 1995.
9. Principles of Sericulture, Hisao Aruga, Oxford & IBH Publish-
ing Co. (P) Ltd., New Delhi, 1994.
10. Pattuparishrama (B.Sc.), P. Srinivas etal., Telugu Akademy,
Hyderabad, 1996.
11. Pattuparishrama (Intermediate), P. Srinivas, Telugu Akademy,
Hyderabad, 1996.
12. Text Book of Tropical Sericulture, Japan Overseas Co-opera-
tion Volunteers, Japan, 1975.
13. A Practical Guide to Mulberry Silk Cocoon Production,
Krishnaswamy, Bangalore, 1994.
14. Sericulture Instructional Cum Practical Manual, Vol.II, NCERT,
New Delhi,1990.
15. Bulletins on Sericulture, C.S.B., Bangalore.
16. Hand Book on Agriculture, ICAR, New Delhi, 1992.
REFERENCE BOOKS
138

17. Hand Book on Pest and Disease Control of Mulberry and Silk-
worm, ESCAP. United Nations, Thailand, 1990.
18. Silk in India, Statistical Biennial, C.S.B., Bangalore,1992.
19. Lecturers on Sericulture by Boraiah, SBS Publishers, Banga-
lore, 1994.
20. Global Silk Secnario-2001 by CSB, Oxford & IBH Publishers,
Bangalore, 1996.
21. Annadata, Telugu Magazines, Vasundara Publications, Eenadu,
Hyderabad.
22. Sericulture, Silk Worm Rearing Techniques, Department of Seri-
culture, Government of A.P., 1991.
139

APPETITE
ASSIMILATION
BIVOLTINE COCOONS
BLEACHING
BREED
BRUSHING
CHAWKI REARING
COCOON
LEAF CHOPPING
DIGESTION
DEBRIS
SPINNERET
DENIER
DFL’s
DISINFECT
GLOSSARY
Behaviour desirous for food
Absorpotion and building up of simple food-
stuffs, or products of digestion of food-stuffs,
into complex constituents of the organism.
It produces white silk, the silkworms have two
generations in a year.
It is a chemical process involved in eliminating
harmful micro-organisms.
Capability to propagate, give birth to.
Process of transferring the newly hatched silk-
worm larvae from egg shells into rearing trays.
Rearing of I,II,III instar silkworms.
Protective covering of eggs, larvae etc.eg.eggs
of some annelide are fertilized and developed
in a cocoon. Larvae of many insects spin co-
coons in which pupae develop.
During early stages of rearing (Chawki) the
worms are fed with finely cut leaves so as to
enable to feed sufficiently.
Breakdown of complex foodstuffs by enzymes
to simpler compounds which can be incorpo-
rated into metabolism.
It is an unwanted, waste product.
A Special organ used to spin the cocoon found
in certain insects.
A number which indicates the weight in grams
of 9000 meters of silk filament/yarn etc.
Disease Free Layings.
The destruction and extermination of disease
causing germs.
140

DIMILIN It is a chemical used to sterilize an animal
especially insects.
ECDYSIS Moulting. In Arthropoda, periodic shedding
inner part of old cuticle is absorbed the rest
is split at line of weakness, and the insect
draws itself out, clothed in a preformed soft
new cuticle. By swallowing air the insect
quickly increases its bulk and the new cu-
ticle finally hardens a size larger than the old.
The lining of all but the finest tracheae is shed
with the old cuticle. Ecdysis in insects is ini-
tiated by a hormone (ecdysone), periodic
ecdysis produce a succession of stages of
growth and development called instars, the
last of which is the adult.
EXCRETION Getting rid products of metabolism either by
storing them in insoluble form by removing
them from body.
FERMENTATION Decomposition of organic substances by or-
ganisms especially bacteria and yeasts. Eg.
Decomposition of sugar forming ethyl alco-
hol and carbondioxide by yeast. Sometimes
means anaerobic respiration.
FLIMSY COCOONS Defective cocoon which possesses very thin
shell consisting little amount of silk.
FLOSS It is the outer most loose, fragmented layer
of cocoon. It is to be removed while reeling.
It is a waste silk.
FYM Farm Yard Manure. It is a manure made by
waste products such as a dung, urine and lit-
ter of farm animals.
GLOSSY LEAF It is the largest leaf found on the top of the
shoot among the first few leaves. It is smooth,
glossy and light green.
141

GOSSAMER LAYER After spinning the compact shell (cocoon) the
shrinking larvae warps itself in gossamer
layer (palade layer) and detaches itself from
the shell to undergo pupation.
GROWTH Increase in size of the body
HATCHING Emergence of developed embryo from egg.
HYGROMETER It is instrument used to measure humidity of
the environment.
HYGIENE It is a state where total healthy conditions are
available.
INSTAR Stage indevelopment of an insect, between
two ecdyses or the final adult stage.
INCUBATION Preparation of eggs for hatching or provid-
ing suitable conditions favourable for uni-
form development of embryo.
LARVA The pre-adult form in which some animals
hatch from the egg; capable of feeding for
itself though usually in a way different from
adult; but usually incapable of sexual repro-
duction and distinctly different from sexu-
ally mature adult in form. Changes into adult,
usually be a rather rapid metamorphosis.
LATE AGE REARING Rearing of IV and V instar worms.
LAYING The total number of eggs laid by a single
silkmoth
METAMORPHOSIS Period of rapid transformation from larval to
adult form. Often involves considerable de-
struction of larval tissues.
MORALITY It denotes the death rate of an organism.
PENTAMOULTERS The larval life stage of an insect moults for
five times.
PHYSIOLOGY Study of the processes which go on in living
organisms.
142

PROTEIN Very complex organic compound, composed
of many amino acids.
PUPA (CHRYSALIS) Stage between larva and adult of
endopterygote insect, in which locomotion
and feeding cease but great developmental
changes occur.
SUCCULENT Having a fleshly appearance.
PROTHETELY Intermediate form between larva and pupa
of an insect.
SILK Afibrous protenous secretion secreted by cer-
tain insects.
SILK GLAND It is a modified salivary gland found in silk-
worms for synthesis of silk, which will be
used to spun the cocoon for undergoing pu-
pation.
GHICHA Yarn drawn by hand out of tasar cocoons
without any twist. Waste mulberry cocoons
are also used for this kind.
KATIA Yarn spun out of tasar and mulberry waste
after opening and cleaning.
143

Silkworm rearing technology

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