Theory notes of Fundamentals of Entomology

Prof. Mochi A. S. (K. K. Wagh College of Agriculture, Nashik)
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Theory Notes on Fundamentals of Entomology
Course No. : ENTO-121
Course Title: FUNDAMENTALS OF ENTOMOLOGY
Course Credit: 1+1=2
Teaching Schedule (Theory):
Lecture
No. Name of Topic
1 & 2 Introduction
* Introduction and history of Entomology including contribution of
scientist in brief (Aristotal, Carlous Linnaeus, Fabricious, Charles Darwin,
Lefroy, Wigglesworth, Snodgrass, Pradhan, Runwal., Pruthi and
Ananthkrishnan.
Definition : Insect & Entomology
Characteristics of Class - Insecta
* Economic importance of insects : harmful, beneficial and productive insects
* Pests of national importance e.g. Locust, termite and white grub along with
their extent of losses.
* Premier Institutes concerned with Entomology :
International – CAB (UK), IOBC(Trinidad), International Institute of
Insect Physiology – Kenya.
National – National Institute of Biological Control (Bangalore)
NCIPM - (New Delhi), CIB (Faridabad), National Plant Protection
Institute, Hyderabad, Indian Grain Storage Institute (Hapur),
3 Dominance of Class Insecta
4 Insect Integument
Structure, chemical composition and functions of Cuticle
Process of moulting, cuticular appendages and processes
5 Body segmentation and structure of Head
Body regions, structure of head capsule, and positions of head and structure of cervix
6 Structure of thorax and abdomen
Segmentation, appendages and processes, pregenital & post genital appendages and
structure of genitalia
7 Structure and modifications of Antennae
Components of typical antenna, basal articulation, functions and modifications (with
examples)
8 & 9 Structure and modifications of mouth parts
Structure and feeding mechanism of Mandibulate type of mouthparts and Haustellate
type of mouth parts (piercing & sucking ; chewing & lapping; sponging; rasping &
sucking and siphoning)
10 Structure and modifications of leg
Components of typical leg, basal articulation, tripod locomotion and modifications
(with examples)
11 Structure and modifications of wings
Basal articulation, regions, hypothetical wing venation, wing coupling apparatus and
modifications (with examples)

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12 Sensory and Sound producing organs
Sensory organs : Location and function (mechanoreceptors, audio receptors chemo
receptors, thermo & humidity receptors, photoreceptors and vision & visual organs,
with examples
Sound producing organs : Tympanum & Stridulatory organs
13 Metamorphosis and Seasonal adoptions
Definition and types of metamorphosis with examples.
Seasonal adoptions (aestivation, quiescence, hibernation and diapauses) with examples
14 & 15 Immature stages of Insects
Structure of egg, eclosion and its type (with examples)
Types of larvae and pupae (with examples); nymphal stage
16 Structure and functions of Digestive system
Alimentary canal: salivary glands, proventriculus, filter chamber, digestion and
absorption of food.
17 Structure and functions of Circulatory system
Organs of circulations, composition of blood and functioning of dorsal vessel
18 Structure and functions of excretory system
Organs of excretion and their functioning; products of excretion
19 Structure and functions of Respiratory system
Organs of respiration and types of respiration (with examples)
20 & 21 Structure and functions of Nervous system
Organs of nervous system, types of neurons and conduction of nerve impulse
22 & 23 Structure of Reproductive systems in Insects
Male and female reproductive systems and types of reproduction
24 & 25 Systematics:
Importance and history of Taxonomy; development of binomial nomenclature along
with its rules and regulations
Definitions : Order, Family, Genus, Species, Sub-species and Biotypes
26 & 27 Classification
Phylum Arthropoda along with its characters
Class Insecta along with its characters
28 & 29 Characters of orders along with families of agricultural importance Orthoptera
(Family: Acrididae), Dictyoptera (Family: Mantidae)
30 & 31 Characters of orders along with families of agricultural importance
Odonata, Isoptera (Family: Termitidae) and Thysanoptera (Family:Thripidae)
32 Characters of orders along with families of agricultural importance
Hemiptera (Family: Pentatomidae, Coreidae, Pyrrhocoridae, Lygaeidae, Cicadellidae,
Delphacidae, Aphididae, Aleurodidae, Coccidae, Psedococcidae
Neuroptera (Family: Chrysopidae), Lepidoptera (Family: Noctuidae, Sphingidae,
Pyralidae, Gelechiidae, Arctiidae.
34 & 35 Characters of orders along with families of agricultural importance
Diptera (Family:Cecidomyiidae, Trypetidae, Tachinidae, Agromyziidae)
Hymenoptera (Family: Tenthridinidae, Apidae, Trichogrammatidae, Ichneumonidae,
Braconidae)
Coleoptera (Family: Coccinellidae, Chrysomelidae, Cerambycidae, Bruchidae,
Scarabaeidae, Curculionidae)

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INTRODUCTION
 The word Insect derived from the Greek word insecare, means cut in pieces or
engraved /segmented.
 Insects belong to the Phylum Arthropoda(Artho= jointed, Poda= Legs) which is
the biggest phylum of kingdomAnimalia. More than three quarters of the animals
on earth are arthropods, and most of these are insects.
 KingdomAnimalia is classified into twelve phyla.
 Insect: -The insects are the tracheate arthropods in which the body is divided in to
head, thorax and abdomen possessing two pairs of wings and three pairs of legs and
single pair of antennae.
 Entomology: -Greek word-(Entomon = Insect; Logos = Study) It is the branch of
zoologyor biological science that deals with the study of insects.
 Branches of Entomology:-
1.) Study and use of insects in crime investigations is known as Forensic Entomology.
2.) Study of insects related to live stock and veterinary animals is known as Veterinary
Entomology.
3.) Study of insects in relation to Human beings is known as Medical Entomology.
HISTORY OF ENTOMOLOGY
 In ancient scripts like Ramayana and Mahabharata, some of the terms used were
related to insects. They are;
 Pipilika – Ant,
 Pathanga – grasshoppers,
 Madhumakshika – honey bees,
 Umbakapalika - termite queen
References of Insects in Ancient Indian Literature
 Mahabharta : (1424 – 1366 BC) Mentions about silk, honey and lac
 The Famous story of “Lakshgruha” i.e. House of Lac build by Kauravas to burn their
cousins live, Pandavas.
 Amarkosha Sanskrit dictionary provide references like Patanga and Bhramar of flies ,
Moths, beetles and Glow worms
 Sushruta : Surgeon (100 - 200 AD) : Classified ants (Pipilika), Mosquitoes and Flies
 Umaswati : Physician (0 - 100 AD) : Classified the Bees
 Pests of national importance –
 E.g. Locust, termite and white grub.

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Contribution of scientist: -
 Aristotle (384-322 B.C.) –
 He was the Father of biological classification.
 First person grouped insects in Mandibulate and Haustellate types and winged and
wing less groups.
 He gave the terms like Coleoptera and Diptera
 Carolus Linnaeus (1758) –
 Father of Taxonomy
 In his publication “Systema Naturae” 1758 includes 28 Indian insect species.
 J. C. Fabricius (1745- 1808) –
 Danish Entomologist described over 10,000 insect species.
 Published “Philosophia Entomologia” in 1778.
 World’s first Text Book in Entomology.
 The first entomologist who made any extensive study of Indian Insects.
 Classified the insects in to 13 orders based on type of mouth parts.
 J.G. Koenig (1767-1779) –
 J.G Koenig was the first to collect number of insects from Coromandel and
Southern India.
 For his memory Red cotton bug is named as Dysdercus koenigi
 Snodgrass R. E. (1875) –
 Great Insect Morphologist referred as a Father of Insect Morphology.
 He wrote book - Principles of InsectMorphology
 Lionel de Nicevelle (1901) –
 Was appointed as the first entomologist to the Government of India.
 Maxwell Lefroy (1903) –
 Was appointed as the second entomologist to the Government of India.
 First Imperial Entomologist
 1906 publication of ‘Indian insect pests’P
 1909 publication of Indian insect life’
 Mithan Lal Runwal (1908) -
 Outstanding work on Termites / White ants
 Contributions to ecology, embryology and Locust study are noteworthy
 Sir Vincent B. Wigglesworth–
 Insect physiologist, work on blood sucking bug, Bed Bug.
 Father of Insect Physiology
 T.B Fletcher (1914) –
 The first Govt. Entomologist of Madras state.
 Wrote a book ‘Some South Indian insects’.
 Second Imperial Entomologist.

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 T.V. Rama Krishna Ayyar (1940) –
 Wrote a book ‘Hand book of Economic Entomology for South India’
 H S Pruthi (1963)–
 1934 - First Indian, Imperial Entomologist of Independent India
 1963 - He become first Plant Protection Advisor to Government of India
 ‘Wrote a Text book of Agricultural Entomology’
 Dr. M.S. Mani's (1968)–
 Wrote a "General Entomology"
 Dr. S. Pradhan(1969) -
 Wrote a "Insect Pests of Crops" and Father of ModernApplied Entomology in
India
 B. Vasantharaj David and T.Kumara Swami (1975) –
 Wrote a‘Elements of Economic Entomology’
 M R G K Nair (1975) –
 Wrote a‘Insects and Mites of crops in India’.
 K.K. Nayar, N. Ananthakrishnan and B. Vasantharaj David(1976) –
 Wrote a‘General and applied Entomology’
 1912- Plant Quarantine Act was enforced.
 1914- Destructive Insects and Pests Act was enforced. (DIPA)
 1916 - Imperial Forest Research Institute Established at Dehradun (Uttarakhanda)
 1925 – Indian Lac Research Institute started at Ranchi, Bihar
 1937 - A laboratory for storage pests was started at Hapur, U.P.
 1937 -Entomology division was started in IARI, New Delhi
 1939 – Locust Warning Organization established
 1946- ‘Directorate of Plant Protection, Quarantine and Storage’ of GOI started.
 1968- The Govt. of India enacted ‘Central Insecticide Act’ which came into force
from 1st
January, 1971.
Establishment of entomological institutes
 IOBC,West Indies(Trinidad)- (International Organization for Biological and
Integrated Control of Noxious animals and Plants)
 ICIPE,Kenya – International Centre of Insect Physiology and Ecology
 NCIPM,New Delhi - (National Centre for Integrated Pest Management - 1988)
 PDBC, Bangalore - (Project Directorate of Biological Control -1993), and thenPDBC
are (NBAII) i.e. National Bureau of Agriculturally Important
Insects(2009)&nowareNBAIR -National Bureau of Agricultural Insect Resources.
 CIB, Faridabad – Central Insecticide Board
 NPPTI, Hyderabad – National Plant Protection Training Institute - 1966
 IGSI, Hapur U.P. - Indian Grain Storage Institute
 1946 Directorate of plant protection Quarantine and storage(DPPQS), Faridabad
 1937 Establishment of Entomology division at IARI New Delhi
 CABI, UK – Commonwealth Agricultural Bureau International

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ECONOMIC IMPORTANCE OF INSECTS
The field of entomology may be divided into 2 major aspects.
1. Fundamental Entomology or General Entomology
2. Applied Entomology or Economic Entomology
 Fundamental Entomology:-
 It deals with the basic or academic aspects of the Science of Entomology.
 It includes morphology, anatomy, physiology and taxonomy of the insects.
 In this case we study the subject for gaining knowledge on Entomology irrespective
of whether it is useful or harmful.
 Applied Entomology or Economic Entomology:-
 It deals with the usefulness of the Science of Entomology for the benefit of
mankind.
 Applied entomology covers the study of insects which are either beneficial or
harmful to human beings.
 It deals with the ways in which beneficial insects like predators, parasitoids,
pollinators or productive insects like honey bees, silkworm and lac insect can be
best exploited for our welfare.
 Applied entomology also studies the methods in which harmful insects or pests
can be managed without causing significant damage or loss to us.
Economic classification of insects
 Insects can be classified as follows based on their economic importance.
1. Insects of no economic importance:-
There are many insects found in forests, and agricultural lands which neither cause harm
nor benefit us.
2. Insects of economic importance:-
A. Injurious insects
a) Pests of cultivated plants (crop pests)
Each cultivated plant damage by many insect pests which feed on them reduces the
yield of the crop. E.g. cotton bollworm, Rice stem bores.
b) Storage pests
Insects feed on stored products and cause economic loss. E.g. Rice weevil, Pulse beetle.
c) Pest attacking cattle and domestic animals
Cattle are affected by pests like Horse fly, Flesh fly, Fleas and Lice. They suck blood and
sometimes eat the flash.
d) House hold and disease carrying insects
House hold pests include cockroach, ants, etc. Disease carrying insects are like
mosquitoes, houseflies, bed bugs, fleas etc.

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B. Beneficial insects
I) Productive insects
i) Silk worm: - The silk worm filament secreted from the salivary gland of the larva helps us
in producing silk.
ii) Honey bee: - Provides us with honey and many other byproducts like bees wax and royal
jelly.
iii) Lac insects: - The secretion from the body of these scale insects is called lac. Useful in
making vanishes and polishes.
iv) Insects useful as drugs, food, ornaments etc.,
(a)As medicine e.g. Sting of honey bees- remedy for rheumatism and arthritis Eanthoridin -
extracted from blister beetle –useful as hair tonic.
(b)As food - for animals and human being. For animals- aquatic insects used as fish food.
Grasshoppers, termites, pupae of moths. They have been used as food by human beings in
different parts of the world.
(c) Ornaments, entertainers
-Artists and designers copy colour of butterflies.
- Beetles worm as necklace.
- Insect collection is a hobby.
(d)Scientific research
Drosophila and mosquitoes are useful in genetic and toxicological studies respectively.
(II) Helpful insects
(i) Parasites: These are small insects which feed and live on harmful insects by completing
their life cycle in a host and kill the host insect. E.g. egg, larval and pupal parasitoids
(ii) Predators: These are large insects which capture and devour harmful insects.E.g.
Coccinellids and Preying Mantid.
(iii)Pollinators: Many cross pollinated plants depend on insects for pollination and fruit set.
E.g. Honey bees, aid in pollination of sunflower crop.
(iv)Weed killers: Insects which feed on weeds kill them thereby killers. E.g. Mexican beetle
eats on Parthenium (Gajar gavat). Cochineal insect feeds in Opuntia dillenii.
(v) Soil builders: soil insects such as ants, beetles, larval of cutworms, crickets, collombola,
make tunnels in soil and facilitate aeration in soil. They become good manure after death
and enrich soil.
(vi) Scavengers: Insects which feed on dead and decaying matter are called scavengers.They
important for maintaining hygiene in the surroundings.E.g. Carrion beetles, Rove beetles
feed on dead animals and plants.
d) House hold and disease carrying insects
i) Pests which cause damage to belongings of human being like furniture, wool, paper etc.
E.g. Cockroaches, furniture beetle, sliver fish etc.
ii) Pests which cause painful bite, inject venoms. E.g. Wasps, bees sting us. Hairy caterpillar
nettling hairs are poisonous. Mosquitoes, bugs bite, piece and suck blood from us.
iii) Disease causing Mosquito- Malaria, Filariasis, dengue fever. Housefly- Typhoid, Cholera,
Leprosy, Anthrax.

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INSECT DOMINANCE
 Measures of dominance:
1. More number of species.
2. Large number of individuals in a single species: e.g. Locust swarm comprising
of 10
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numbers of individuals, occupying large area.
3. Great variety of habitats
4. Long geological history
 Reasons for dominance:
There are several structural, morphological and physiological factors responsible for
insect dominance. They are:
1. Capacity for flight
2. More adaptability or universality smaller size: Majority of insects are small
in their size conferring the following physiological and ecological advantages.
3. Presence of exoskeleton: Insect body is covered with an outer cuticle called
exoskeleton which is made up of a cuticular protein called Chitin. This is light
in weight and gives strength, rigidity and flexibility to the insect body.
4. Resistance to desiccation: Insects minimize the water loss from their body
surface through prevention of water loss (wax layer of epicuticle, closable
spiracles, egg shell) conservation of water (capable of utilizing metabolic
water, reabsorption of water from fecal matter, use less quantity of water to
remove the nitrogenous waste)
5. Tracheal system of respiration: This ensures direct transfer of adequate
oxygen to actively breathing tissues. Spiracles through their closing
mechanism admit air and restrict water loss.
6. Higher reproductive potential: Reproductive potential of insect is high e.g.
Egg laying capacity (fecundity) of queen termite is 6000 - 7000 eggs per day
for 15 long years. Short development period e.g., Corn aphid produces 16
nymphs per female which reaches the adulthood within 16 days. Presence of
special types of reproduction other than oviparity and viviparity like
Polyembryony, Parthenogenesis and Paedogenesis.
7. Presence of complete metamorphosis: More than 82 per cent of insects
undergo complete metamorphosis (holometabolous insects) with four stages.
As the larval and adult food sources are different, competition for food is less.
8. Presence of defense mechanisms: By different defense mechanisms, insects
escape from the enemies to increase their survival rate.
9. Hexapod locomotion: Insects uses 3 legs at a time during locomotion, while
the remaining 3 legs are static, which gives greater stability.

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INSECT INTEGUMENT
 The vertebrates have internal skeleton known as endoskeletonwhile in insects it is
located outside the body forming exoskeleton.
 Insect cuticle provides space for attachment of muscles of antenna and mouthparts,
called as tentorium.
 Insect body wall iscalled as Integument or Exoskeleton. It is the external covering of
the body which is ectodermal in origin. It is rigid, flexible, lighter, stronger and
variously modified in different body parts to suit different modes of life.
 Integument consists of 3 layers:-
1) Cuticle (Upper)
2) Epidermis (or) hypodermis(Middle)
3) basement membrane (Inner)
1. Cuticle:-
 It is outermost thick layer of integument secreted by epidermis.
 It is non-cellular.
 It is divided in to two regions:-Epicuticle (Upper) and Procuticle(Inner)
A. Epicuticle:
 It is a thin outermost layer varying in thickness from 1-4μ. Chitin is absent in
epicuticle.It consists of the following 4 layers

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 Cement layer:It is secreted by dermal glands and is composed of lipoprotein.It
protects the body from external damage.
 Wax layer: Itconsisting of long chain hydrocarbons, esters of fatty acids and
alcohols. It serves as water proof layer preventing water loss from the body
 Polyphenol layer: It is a non-static layer containing various types of phenols
which are mainly used in the formation of the proteins.It is resistant to acids and
organic solvents.
 Cuticulin layer: It is an amber coloured thin layer over the surface of the
epidermis which is strengthened by outer polyphenol layer.It serves the purpose of
permeability and also acts as growth barrier.
B. Procuticle:
 It is differentiated in to exo and endocuticle.
 Exocuticle: It is darkly pigmented, hard and sclerotized. This layer is made up of
chitin and sclerotin.
 Endocuticle: It is soft, light coloured and unsclerotized. This layer is made up of
chitin and arthropodin.
 Pore canals: These are numerous fine vertical channels traversing both exo and
endocuticle. Pore canals present in the exocuticle helps in the deposition of epicuticle.
They are useful in transportation of cuticular material and enzymes to the outer pro
and epicuticle parts.
 Composition of cuticle:
♣ Two major components of insect cuticle are; i) Chitin,ii) Proteins.
i) Chitin:
 It is a nitrogenous polysaccharide.
 It consists of high molecular weight polymer of anhydro-N-acetyl glucosamine
residues joined by β-glycosidic linkages.It is water insoluble but soluble in dilute
acids, alkalies and organic solvents.
ii) Proteins:Cuticle has 3 types of proteins
 Arthropodin:An untanned protein means it is soft water soluble protein present in
endocuticle. The conversion of arthopodin in to sclerotin is known as sclerotization or
tanning.
 Sclerotin:It is also called tanned protein which is amber coloured and present only in
exocuticle.This is water insoluble.
 Resilin:It is a rubber like elastic protein which is colourless and present in joints such
as wing hinge ligaments, leg joints, clypeolabral joints or suture and tergosternal
joints.

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2. Epidermis (or) hypodermis:
 It is an inner unicellular layer resting on basement membrane with the following
function.
i. Cuticle secretion
ii. Digestion and absorption of old cuticle
iii. Wound repairing
iv. Gives surface look
 Adjacent epidermal cells are held together by means of certain cytoplasmic processes
which are known as desmosomes.
 All the epidermal cells are glandular and secrete cuticle and the enzymes involved in
production and digestion of old cuticle during moulting.
 The epidermal cells get differentiated in to following types based on the function they
perform and may modify in to;
a)Dermal glands producing cement layer
b)Trichogen cell producing hair like seta or trichome.
c)Moulting glands secreting moulting fluid which digests the old cuticle
d)Peristigmatic glands around the spiracles in case of Dipteran larvae
3. Basement membrane:
 It is the basal part of the body wall formed from degenerated epidermal cells and
appears as non-living amorphous (shapeless) granular layer of integument.
 It is about 0.5µ in thickness and consists of fibrous protein, glycosaminoglycans
which are polymers of disaccharides.
 The basement membrane forms a continuous sheet beneath the epidermis, where
muscles are attached and become continuous with sarcolemma of the muscles.
Functions of Insect Integument
o It provides protection to the internal organs enclosed by it.
o It gives shape and size to the insects.
o It provides surface for the attachment of muscles.
o It conserves moisture and prevents desiccation.
o It prevents entry of pathogens and insecticides.
o It forms sense organ.
o It contains pigments to make insects attractive.

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CUTICULAR/ INTEGUMENTAL MODIFICATIONS:
Cuticular modification
A. Cuticular out growths:
 They are divided into cuticular appendages and cuticular processes depending on
the presence or absence of membranous articulations.
I. Cuticular appendages:
 These are the outgrowths of the cuticle / integument connected with it by means of a
membranous joint. They arise from modified epidermal cells. These are classified in
to setae and spurs.
(1) Seta/ Macrotrichia:
♣ Commonly known as hairs and arise from a cup like alveolus or pit. Setae are hollow
structures developed as extension of exocuticle and are produced by a single enlarged
hypodermal cell called ‘ trichogen’ cell. Articular membrane is usually produced by a
second hypodermal cell called ‘tormogen’ cell.
♣ Setae have role of taxonomic importance and vary with species to species. Study of
arrangement of setae is known as ‘chaetotaxy’.
(2) Spurs:
♣ Occur on the legs of many insects and differ from setae in beingmulticellular in
origin.
II. Cuticular processes:
 They have no membranous articulation; They are of two types
(1) Microtrichia / fixed hairs / aculei:
♣ These are minute hair like structures found on wings of Mecoptera and certain
Diptera.
(2) Spines:
♣ Outgrowths of the cuticle which are more or less thorn like in form.
Cuticular
out growths
Cuticular
invagination
Apodemes
Apophyses
Cuticular
appendages
Cuticular
processes
Setae
Spurs
Aculei
Spines

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Sr.
No.
Spurs Spines
1 Cuticular appendages Cuticular processes
2 Movable, multicellular structures and thick
walled
These are immovable outgrowths of cuticle
3 E.g.: present on tibia of plant hoppers and honey
bees
E.g.: hind tibia of grasshopper and leaf
hoppers
B. Cuticular invagination:
 The body wall or cuticle of the body wall invaginate internally and grow in to definite
structures which are of two types.
♠ Apodemes- Hollow cuticular invaginations whichprovide area for muscle attachment
♠ Apophyses- Solid invaginations of the cuticle which gives mechanical support to
various organs by forming distinct skeletal structures.
MOULTING PROCESS
 Process of periodical shedding of old cuticle and formation of new cuticle this process
is known as moulting. Itis a complex process which involves: - Apolysis, Ecdysis and
Sclerotization.
 Apolysis : [Apo = formation ; Lysis = dissolution]
 The dissolution of old cuticle and formation of new one is known as apolysis.
 It starts with repeated mitotic division of epidermal cells resulting in increase in
number and size of epidermis, Because of this change, the epidermal cells exert
tension on cuticular surface and as a result get separated them from the cuticle.
 Due to separation of epidermis from the cuticle a sub cuticular space is created and
the epidermal cells starts producing their secretion i.e. moulting fluid and cuticular
material into this space.
 Ecdysis :
 The stage where the insect has both newly formed epi and procuticle.
 The ecdysial membrane starts splitting along the line of weakness due to muscular
activity of the inner developing insect and also because of swallowing of air & water
resulting in the distention of the gut and also due to the pumping of blood from
abdomen to thorax through muscular activity.
 After the breakage of old cuticles, the new instar comes out bringing its head followed
by thorax, abdomen and appendages.
 Sclerotization :
 After shedding of old cuticle the new cuticle which is soft, milky white coloured
becomes dark and hard through the process known as tanning (or) sclerotization.
 Three types of hormones involved in the process of moulting which are as follows-
 JH: Juvenile Hormone: Produced from corpora allata of brain that helps the insects
to be in immature stage.
 MH: Moulting hormone: Produced from prothoracic glands of brain that induces the
process of moulting.
 Eclosion Hormone: Released from neurosecretory cells in the brain that help in the
process of ecdysis or eclosion.

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BODY SEGMENTATION OF INSECT
 Cockroach, Periplanata americana is a typical insect as it possesses all important
characters of class insect.
 In general, insect body is divided in to a series of rings or segments are known as
“somites” or “metameres”.
 During the process ofevolution, these somites get fused with each other in different
ways forming the body parts of the existing arthropods.
 The type of arrangement of these body segments in embryonic stage is known as
primary segmentation while in adult insects is known as the secondary
segmentation.
 Insect body is divided in to three regions or tagmata namely head, thorax and
abdomen. This grouping of body segments in to regions is known as tagmosis.
 Head consists of 6 segmentspossessesmouthparts, compound eyes, simple
eyes (ocelli) and a pair of antennae.
 Thorax consists of 3 segments i.e. prothorax, mesothorax and metathorax,
Meso and metathorax are together known as pterothorax. All the three thoracic
segments possess a pair of legs and meso and meta thorax possess one pair of
wings.
 Abdomen has 11 segments with genital appendages on 8th and 9th
segments.
 The insect body generally consists of 20 segments.
Fig. General Organization of Insect Body

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INSECT HEAD
 It is the foremost part in insect body consisting of 6 segments that are fused to form a
head capsule.
 The head segments can be divided in to two regions i.e. procephalon and
gnathocephalon (mouth).
 Head is attached or articulated to the thorax through neck or cervix.
 Head capsule is sclerotized and the head capsule excluding appendages formed by the
fusion of several sclerites is known as cranium.
 Inside the head, an endoskeletal structure called the tentoriumwhich give supports to
the brain, and provides a rigid origin for muscles of the mandibles and other
mouthparts.
 Head is concerned with feeding and sensory perception.
Segment Appendages
I Pre antennary segment Procephalon Pair of compound eyes&
three ocelli (Simple eyes)
II Antennary segment Pair of Antennae
III Intercalary segment Single labrum
IV Mandibular segment Gnathocephalon Pair of Mandibles
V Maxillary segment Pair of Maxillae
VI Labialsegment Single Labium
Types of head position:
The orientation of head with respect to the rest of the body varies. According to the
position or projection of mouth parts the head of the insect can be classified as;
(a) Hypognathous (Hypo – Below: Gnathous – Jaw )
The head remain vertical and is at right angle to the long axis of the body and mouth
parts are ventrally placed and projected downwards. This is also kwown as Orthopteroid type.
Eg: Grass hopper, Cockroach.

16
CockroachGrass hopper
(b) Prognathous : (Pro – infront: Gnathous – Jaw )
The head remains in the same axis to body and mouth parts are projected forward.
This is also known as Coleopteroid type.Eg: beetles
Beetles
(c) Opisthognathous : (Opistho – behind: Gnathous Jaw )
It is same as prognathous but mouthparts are directed backward and held inbetween the fore
legs. .This is also kwown as Hemipteroid or Opisthorhynchous type.Eg: bugs

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Mosquito Red cotton bug
SCLERITES AND SUTURES OF HEAD
The head capsule is formed by the union of number of sclerites or cuticular plates or areas
which are joined together by means of cuticular lines or ridges known as sutures or any of
the large or small sclerotized/harden areas of the body wall.
These sutures provide mechanical support to the cranial wall.
Suture: The sclerites separated from each other by means of thin impressed line called
suture.(Sometimes referred as a sulcus).
General insect possess the following sclerites-
1. Labrum:It is small sclerite that forms the upper lip of the mouth cavity. It isfreely
attached clypeus by means of clypolabral suture.
2.Clypeus:It is situated above the labrum, separated by fronto-clypeal suture & also
separated from gena by clypogenal suture.
3.Frons: It is unpaired, facial part of the head capsule lying between the arms of
epicranial suture.
4. Gena: It is the area extending from below the compound eyes to just above the
mandibles. It is separated from frons by frontoganal suture and from clypeus clypogenal
suture.
5. Epicraniun: It forms the upper part of the head extending from frons to the neck.

18
6. Vertex: It is the top portion of epicranium which lies behind the frons or the area
between the two compound eyes.
7. Epicranial Suture: Starting from the dorsal portion of the epicranium is an inverted Y
shape suture known as epicranial suture or ecdysial line. The head capsule breaks open
along this line at the time of moulting.
8. Occiput: It is an inverted “U” shaped structure representing the area between the
epicranium and post occiput.
9. Post occiput: It is the extreme posterior part of the insect head that remains before the
neck region.
10. Occular sclerites: These are cuticular ring like structures present around each
compound eye.
11. Antennal sclerites: These form the basis for the antennae and present around the
scape.
Anterior view or face view
The common sutures present in head are:
1. Clypeolabral suture:It is the suture present between clypeus and labrum.
2. Clypeofrontal suture or epistomal suture: The suture present betweenclypeus and
frons.
3. Epicranial suture: It is an inverted ‘Y’ shaped suture distributed above thefacial
region extending up to the epicranial part of the head. It consists of two arms called
frontal suture occupying the frons and stem called as coronal suture. This epicranial
suture is also known as line of weakness or ecdysial suture because the exuvial
membrane splits along this suture during the process of ecdysis.
4. Occipital suture: It is ‘U’ shaped or horseshoe shaped suture between epicranium
and occiput.

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5. Post occipital suture: It is the only real suture in insect head. Posterior end of the
head is marked by the post occipital suture to which the sclerites are attached. As this
suture separates the head from the neck, hence named as real suture.
6. Genal suture: It is the sutures present on the lateral side of the head i.e. gena.
7. Occular suture: It is circular suture present around each compound eye.
8. Antennal suture: It is a marginal depressed ring around the antennal socket.
INSECT THORAX
 It is the middle part of the body consisting of 3segmentssuch as prothorax,
mesothorax and metathorax, each possessing a pair of legs and a pair of wings on
meso and meta thoracic segment. Meso and meta thoracic segments bear a pair of
wings each together known as pterothorax (Ptera = wings).
 Thorax generally concerned with locomotion.
 The body wall of a typical insect is divided into four regions;
 The dorsal (Upper) region is called dorsum or tergum/notum.
 |The ventral (Lower) region is called as venter or sternum.
 The two lateral regions are known as pleurae/pleuron.
 Sclerites–The cuticle hardens at localized areas form sclerites.

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 Sutures – The sclerites are separated from each other by means of thin impressesd
lines called as sutures.
 Sclerites forming these regions are called as tergites, sternites and pleurites,
respectively.
 Sclerites of thoracic segments:-
1. Sclerites of tergum (tergites) - The dorsal sclerites consists of three
segmental plates (nota) called pro-notum, meso-notum and meta-notum. Each
notum is again divided into three parts i.e pre-scutum, scutum and scutellum.
2. Sclerites of pleuron (pleurites) –it is fully developed in winged insects. It is
divided into two parts, anterior episternum and posterior epimeron. It is absent
in prothorax.
3. Sclerites of sternum (sternites)–It is divided into eusternum and
spinasternum.
INSECT ABDOMEN
 The abdomen in the embryo usually consists 11 segments.
 The abdominal segments are sometimes designated as uromeres.
 The terminal region of abdomen is called telson which bears anus.
 The 1st abdominal segment gets fused to metathorax forming propodeum. (In ants,
bees and wasps).
 The first eight abdominal segments carry a pair of spiracles each.
 Thorax generally concerned with reproduction and metabolic activity.
 Appendages of abdomen–
1. Non reproductive appendages –
a) Cerci –They are present on 11th
segment in most of the insects. It is
present inmale cockroach, silverfish, grasshopperCerciusuallyact as
tactile organ or sound receptors in grasshopper. They become a part of
male genitalia in caddis fly. In earwigs, cerci are modified into
defensive organ.
b) Prolegs in insect larvae- The larvae of Lepidoptera bear five pairs of
abdominal legs called Prolegs on 3rd
4th
5th
6th
and 10th
segments.
These Prolegs bear spines like structures called crochets, on terminal
ends to grip the plant surfaces. In case of larvae of sawfly there are
eight pairs of Prolegs but are without crochets.
c) Abdominal gills-
It is present in aquatic insects for respiration. eg. Nymph of odonata.
d) Cornicles: Aphids have a pair of short tubes known as cornicles or
siphonculi projecting from dorsum of fifth or sixth abdominal segment.

21
They permit the escape of waxy fluid which perhaps serves for
protection against predators.
2. Reproductive appendages –
 It includes abdominal Segments from 1 to 7 are pregenital
segments, 8th
and 9th
are known as genital segments as they
form genital appendages i.e. ovipositor in females and aedeagus
or penis in males. 10th
and11th
segments are known as
postgenital segments. These organs are specially concern with
mating in male and deposition of eggs in females. They are
collectively called as external genitalia or gonapophysis.
 Male external genitalia-The9th
sternum bears two styli and
pair of claspers which help to hold female during copulation.
The aedeagus lies between claspers.
 Female external genitalia-It has a special egg laying organs
called ovipositor for egg lying on 8th
and 9th
segments.The
ovipositor of house fly& fruit fly is called pseudoovipositor.
INSECT ANTENNAE
 Antennae are a pair of sensory preoral appendages arising from the 2nd
or antennal
segment of the head possessing nerves coming from deutocerebrum of the brain.
 Antennae are also called feelers.
 They are well developed in adults and poorly developed in immature stages.
 Antennae are absent in order protura and class Arachnida whereas 2 pairs of
antenna (antennules) are present in class Crustacea.
 Aantennal socket (antennifer) is provided with an antennal suture. The base of socket
is connected to the edge of the socket by an articulatory membrane. This permits free
movement of antennae

22
 Antenna consists of 3 parts:-
1) Scape: It is the first segment of antenna. It articulates with the head capsule through
antennifer which provides movement for the scape.
2) Pedicel: It is the 2nd or middle segment of antenna that forms a joint between scape and
flagellum. It consists of the special auditory organ known as “Jhonston’s organ”.
3) Flagellum: It is the last antennal segment which consists of many segments that varies in
shape and size.
Types of Insect antennae
SrN
o.
Type of antennae Example
1 Filiform (Thread like) Grasshopper
2 Setaceous(Whip/ bristle like) Cockroach
3 Moniliform (Like string of beads) Termites& Thrips
4 Pectinate (Comb like) Female mulberry silk
moth
5 Bipectinate (Double comb) Male mulberry silk moth

23
6 Serrate(Saw like) Pulse beetle, Mango stem
borer
7 Clavate (Clubbed) Butterflies, Moths
8 Clavate with hook Skipper butterflies
9 Capitate (Clubbed with knob) Red flour beetle
10 Geniculate (Elbowed) Ants, honey bees, Wasps
11 Lamellate (plate like) Rhinoceros beetles, dung
rollers,chaffer beetles
12 Plumose(Feather like) Male Culex mosquito,
stylopids
13 Pilose (brush like hairs) Female Culex mosquito
14 Aristate (antennae with arista) House fly
15 Stylate (antennae with style) Jassids, Robber fly
Term Mean
1. Gustatory Related with stimulus of taste
2. Olfactory Related with stimulus of smell
3. Tactile Related with stimulus of touch

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Functions of Antennae
1. To feel and find the its way
2. To detect danger
3. To find food
4. To find the opposite sex
5. To communicate with each other e.g. (Ants)
6. To smell – bears olfactory organ e.g. (House fly)
7. To perceive the sound Chorodontonal organe.g. (male mosquito)
8. To serve secondary sexual characters
9. It possesses hydro fuse hairs to form air funnel eg. (Water beetle)
10. Taste hairs occur on antennae e.g. (Cockroach)
11. Helps in mating by holding opposite sex eg. (Flea, Spring tails)
12. Useful for clasping the female during copulation

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STUDY OF INSECTS MOUTH PARTS
Typical mouthpart of an insect consists of the following parts.
(i) Labrum (upper lip)
(ii) A pair of mandibles (upper Jaw)
(iii) A pair of maxillae (lower Jaw)
(iv)Labium (lower lip)
(v) Hypopharynx (tongue)
 The mouth parts of insects can be basically grouped in to following types based on the
type of food and method of feeding.
Type of Mouth parts
Sr.
No.
Type of Mouth parts Examples
I (Mandibulate type) Those insects feeding on solid food material.
1. Chewing and Biting type Grasshoppers, cockroachesBeetles, Lepidopterous
larvae.
II Sucking type / Haustellate type Those insects feeding on liquid food material.
1.Piercing and sucking type Plant Bugs and Mosquitoes
2.Rasping and sucking type Thrips
3.Sponging type Adult Houseflies
4.Chewing and lapping type Honey bees
5.Siphoning type Butterflies and moths
III Other types
1. Mask type Naids of Dragonflies
2. Degenerate type Maggots of Diptera

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MANDIBULATE TYPE OF MOUTH PARTS
 Those insects feeding on solid food material such as leaves, fruits, tree bark.
I) CHEWING AND BITING TYPE OF MOUTH PARTS
E.g. Grass hopper, Cockroach, Beetles, Lepidopterous larvae
(a) Labrum:
 It is a single unpaired that forms the upper lip of the mouth cavity.
 It protects the mandibles and helps in closing of the mouth cavity and guides the
food in to mouth or hold the food material while feeding.
 Labrum hangs down from the clypeus through a clypeo-labral suture.
 The inner surface of labrum is lined by small lobe like epipharynx, which is the
taste organ.
(b) Mandibles:
 These are the paired, unsegmented, and strongest and sclerotized structures
calledfirst pair of jaws.
 They are attached to the head capsule by means of two joints known as ginglymus
and condyle.
 They possess teeth like molars and incisors that help in the process of cutting the
food material.
 Each mandible is moved by powerful Abductor and adductor muscles.

27
(c) Maxillae:
 These are paired and also known as second pair of jaws.
 These are homologous structures with basal triangular ‘cardo’, middle rectangular
‘stipes’ and the lateral ‘palpifer’ bearing maxillary palpi and lobe like inner
‘lacinia’ and outer ‘galea’. Maxillary palps possess olfactory and gustatory sense
receptors and function as sensory organs. These Galea and lacinia helps in holding
the food material along with the mandibles.
(d) Labium:
 It is known as lower lip and is also called as second maxillae. It closes the mouth
cavity from below.
 It is divided in to proximal prementum. centralmentum and distal
submentumPrementum has three terminal lobes.
 Near the base of pre mentum, on either side lobe like ‘palpiger’ is present which
bears labial palps. The median pair is ‘glossae’ and outer ‘paraglossae’ together
called ligula that function mainly as gustatory sense organs.
(e) Hypopharynx:
 It is a tongue like structure situated between labrum and labium and ducts of
salivary glands open on or near its base. The function of hypopharynx is to
mix saliva with the food material.
HAUSTELLATE TYPE OF MOUTH PARTS
 Those insects feed on liquid food material such plant sap, fruit juice, blood etc
1. PIERCING AND SUCKING TYPEOF MOUTH PARTS
 e.g.: plant bugs, mosquitoes
 They are mainly adopted for piercing the tissues and sucking either plant sap or the
nectar or blood from the host.

28
a) Labrum :
 Labrum is modified into a small flap like structure at the base of rostrum.
b) Mandibles & maxillae:
 Mandibles and maxillae are modified in to sharp needle like stylets. (Four in
numbers)
 The mandibular stylets form the outer pair and possess serrated margins at
their tip.
 The maxillary stylets forms the inner pair having smooth curved tips and
combining together enclosing a food channel.
 The food channel is divided in to an upper cibarium and lower salivarium with
the help of the grooves present inside the maxillary stylets. Salivarium is used
for releasing the saliva and cibarium is used for sucking the sap.
c) Labium :
 Mouth parts are represented by rostrum/beak/Proboscis which is a
modification of Labium.
 It acts as a pouch for protecting the mandibular and maxillary stylets.
 Rostrum has sensory hairs at its tip for sampling the food and locating spot for
piercing.
d) Hypopharynx :
 The hypopharynx is modified in to a pharyngeal pump and is situated at the tip
of the food channel.
 Feeding Mechanism:
 At rest proboscis is always held parallel to ventral side of insect body.
 During feeding the rostrum shot out, stylets released and rostrum looped behind to
allow the stylets to penetrate plant tissues.
 Mandibular stylets by their sliding movement puncture a hole in plant tissues. Then
maxillary stylets are pushed inside.
 Saliva is injected through salivary channel to dilute the cell sap, dissolve the cell wall.
 Then suck the contents (sap/ blood / nectar) through cibarium with the action of
pharyngeal and cibarial muscles.
2. RASPING AND SUCKING TYPE OF MOUTH PARTS E.g. Thrips
 Insect like thrips lacerate the epidermis of plant parts and suck the oozing cell
sap.
 These are called asymmetrical type, since right mandible is rudimentary or
reduce or absent whereas the left mandible is modified in to a mandibular
stylet hence left mandible is present.
 Maxillae are modified in to maxillary stylets which are mainly useful for
sucking the sap that is released outside due to the rasping of tissues by the left
mandible.

29
3. SPONGING TYPE OF MOUTH PARTS: - e.g.: housefly
a) Labrum:
 It is represented by labrum epipharynx.
 It forms stylet.
 It is born on anterior face of haustellum.
b) Mandibles:They are entirely absent.
c) Maxillae:They are represented by a pair of maxillary palps.Maxillary palpi are 1-3
segmented
d) Labium :
 These mouthparts are represented by proboscis formed from the labium.
 The proboscis is divided into a basal rostrum, middle haustellum and
adistallabellum.
 The labellum is a sponge like structure. It is traversed by a number of narrow
transverse channels called pseudotrachea which converge at one point in the
centre of the labellum. From this point, the food enters in to food channel
which is formed by the labrum- epipharynx and hypopharynx.
e) Hypopharynx :
 It is also modified into stylet like structure and is present on haustellum.
 During feeding, the proboscis is pressed over the food material.
 The pseudo trachea gets filled with the food material by the capillary action which
converges at one point in the centre of the labellum.
 From this point, the food enter in to food channel which is formed by the labrum-
epipharynx and hypopharynx and is sucked up from the central point in to the
oesophagus.

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4. CHEWING AND LAPPING TYPE OF MOUTH PARTS:e.g.: honey bees
 The labrum and mandibles are biting type whereas maxillae, labium and hypopharynx
combine together to form a sucking proboscis.
a) Labrum:It is narrow plate attached to clypeus.
b) Mandibles:The mandibles are dumbbell shaped, used for molding wax and
squeezing the nectar.
c) Maxillae :
 Both maxillae are modified and suspended from head.
 They are articulated through like cardo to which is attached stipes.
 The maxillary palpi are very small or reduced and it is peg like structure
articulating with stipes.
 The cardo of maxillae unite with submentum of labium forming an inverted
“V” shaped lorum.
 Galea and lacinia attached at the lorum.
d) Labium :It is also called as proboscis and consist of following parts;
 Submentum (lorum),mentum, prementum, labial palp and glossa.
 Glossae are provided with long hairs and a small spoon shaped lobe, called
flabellum or bouton at its apex.
 Two paraglossa are cup like structure situated at the base of glossa.
e) Hypopharynx:It is vestigial or reduces.
 When at rest the mouthparts are folded down beneath the head.
 During feeding they become straight and shot out glossae and lick the nectar
with the help of flabellum.
 The glossal toung thus smeared with nectar is rapidly retracted between labial
palp and galeae.
 As a result the nectar is squeezed off and deposited in a small cavity formed
by paraglossae and sucked in by the capillary action of pharyngeal pump.

31
5. SIPHONING TYPE OF MOUTH PARTS: e.g.: Moths and Butterflies.
 These are specially modified for taking nectar from the flowers.
 The galea of maxilla form into a slender, hollow, tubular structure which remains as
an elongated coiled proboscis underneath the head during non feeding.
 Mandibles are totally absent.
 The labrum and maxilla palpi are reduced.
 Labium is modified in to a small basal plate possessing 3 segmented labial palps.
 The food channel is formed by the fusion of both the galeae.
 The nectar will be sucked from the flowers through muscular action

32
STUDY OF INSECT LEG
 Insect legs are paired; hollow more or less cylindrical and jointed outgrowth of
thoracic segments. They are the important locomotory organ.
Components of Insect Leg
Fig. Structure of Typical Insect Leg
Insect leg mainly consists of 5 parts viz.
1. Coxa: It is the functional basal segment and it is rigidly fixed to thorax.
2. Trochanter: It is very small and the second segment. It is articulated with coxa and fixed
to femur.
3. Femur: It is the largest, strongest segment and is articulated with the tibia..
4. Tibia: It is equal or more than the length of the femur, articulated with tarsus.
5. Tarsus: it is the largest segment of the leg and usually devided into sub segments
tarsomeres. The number of tarsomeres vary from 1-5. The tarsus at its end consists of
pretarsus which is in the form of a pair of claws and cushion like pulvilli. In between the
claws, if there is lobe like structure, it is known as “arolium” as in Orthoptera (grass hopper)
and if it is bristle like structure, it is called “embodium” as in Diptera.
 Legs of Larvae: Prolegs
 Thoracic legs mean true legs and abdominal legs mean Pseudo legsor false leg
of larvae.There are two to five pairs.
 Abdominal legs are thick, fleshy and unsegmented and the tip (Planta) bear
hooks called crochets, which help in cling the plant surface.

33
MODIFICATIONS OF LEGS IN DIFFERENT INSECTS
Type Legs modified Example purpose
Cursorial All legs Blister beetle, wasp Walking
Ambulatorial All legs Cockroach Running
Saltatorial Hind legs Grasshopper , gryllids Leaping and jumping
Fossorial Front legs Mole crickets, dung rollers Digging
Raptorial Front legs Preying mantids Preying (grasping )
Natatorial Hind legs Water beetle, water bugs Swimming
Scansorial All legs Head louse clinging
Prehensile All legs Dragon flies Catching prey,
basketForming type
Antennal
cleaning legs
Front legs Honey bee For cleaningantennae
Pollen basket
and brush type
Hind legs Honey bee For collectingpollen
and cleaning the
body
Fig. Modification of insect legs

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STUDY OF INSECT WINGS
 Based on the presence or absence of wings, class insecta is divided into two
subclasses; 1. Apterygota &2. Pterygota
o The primitive apterygotes are wingless. E.g.: Silver fish and spring tails.
o Secondarily wingless insects: Among pterygotes, some insects in their advanced stage
of growth (Adult) shed the wings e.g. Bed bugs, head louse.
 Based on the degree of development of wings the insects may be classified into three
forms; 1) Macropterous, 2) Brachypterous & 3) Apterous.
 The insect wings may sometimes possess some pigmented spot near coastal margin
known as pterostigma or stigma as in Odonata (dragon flies and damsel flies).
Fig. Insect wing areas
 A typical insect wing is triangular with three margins and three angles.
 The anterior margin strengthened by the costa is called coastal margin and the
lateral margin is called apical margin and the posterior margin is called anal margin
 Three angles are,
 Humeral angle: between body wall and costal margin
 Apical or outer angle: between costal and apical margin
 Anal angle or tornus : between apical and anal margin
 Wings area are;
 The surface area of typical insect wing is divided in to two portionsi.e.Remegium and
Vannal Area.
 The anterior (upper) part of the wing towards coastal margin where more no of
longitudinal veins are present is called remigium.
 The posterior part of the wing where veins are sparsely distributed is known as
Vannal Area, which is called as clavus in forewings and vanus in hindwings.
 Jugum is the inner most portion of the wing that is cutoff from the main wing by
jugal fold.
 Wings are very thin broad leaf like structures strengthened by a number of hollow
narrow tubular structures called veins.

35
 Arrangement of veins on wing surface is known as Wing venation, which consists of
two types of veins;
1. Longitudinal veins: Extend from base of the wing to the margin. They may be convex (∩)
or concave (U)
2. Cross veins: That interlinks the longitudinal veins.
Fig. Hypothetical wing venation
Longitudinal veins:
1. Costa (C): It forms the thickened anterior margin of the wing (costal) and isun-branched
and is convex
2. Sub costa (Sc): It runs immediately below the costa always in the bottom ofa trough
between C and R. The two branches of SC are Sc1 and Sc2 and is concave
3. Radial vein (R): It is the next main vein, it divided in to two branches R1 and Rs (Radial
sector). R1 goes directly towards apical margin and is convex; Rs is concave and divided in
to 4branches, R2, R3, R4, and R5.
4. Media (M) It is divided in two branches 1. Media anterior (MA) which is convex and2.
Media posterior (MP) and is concave. Media anterior is again divided into MA1 and MA2.
Median posterior is again divided in to MP1, MP2, MP3, and MP4.
5. Cubitus (Cu): Cubitus is divided into convex CU1 and concave CU2. CU1 is again
divided into CU1a and CU1b.
6. Anal veins (A):These veins are convex. They are individual un-branched, 1-3 in number.1
or 2 jugal veins (unbranched) are present in the jugal lobe of the forewing

36
Cross veins: - Small veins often found inter connecting the longitudinal veins are
called cross veins.
 Humeral cross vein (h):between costa and subcosta.
 Radial cross vein (r): between radius and radial sector.
 Sectorial cross veins (s): between sub branches of radial sector.
 Radio medial cross vein (r-m): between radius and media.
 Medical cross veins: between branches of media.
 Medio-cubital veins: between media and cubitus.
DIFFERENT TYPES OF WINGS
1. Tegmina:Forewings are leathery and tough. They are protective in function. They protect
the membranous hindwings. They are not used for flight.e.g.: forewings wings of cockroach,
grasshopper
2.Elytra: The wing is heavily sclerotised without clear venation. Wing is tough and it is
protective in function. They protect the membranous hind wings and abdomen. e.g.:
Forewings beetles and weevils.
3.Hemelytra: The base of the wing is thick like elytra and the remaining half is membranous.
They are not involved in flight and are protective in function. e.g.: Forewings of bugs.
4.Membranous: Naked thin with clear venation. e.g.: Both the wings of Dragonflies, bees
and wasps, Hind wings of grasshopper, beetles,cockroach, both fore wings and hind wings of
(wasp, bees, dragonfly and damselfly).
5. Scaly wings: Wings thin, membranous but covered with unicellular scales all over the
surface. Scales are responsible for colour. e.g.: Both the wings of moths and butterflies.
6. Fringed wings: Wings are highly reduced with reduced venation. The wings are fringed
with long marginal hairs giving a feather like appearance e.g. both the wings of thrips
7. Fissured wings: Forewings are longitudinally divided twice forming a fork like structure
whereas hindwings are divided twice in to three arms. All the forks possess small marginal
hairs.e.g.: Both the wings of plume moth
8. Halteres: In houseflies the hind wings are modified into small microscopic structures/
knobbed vibrating organs called haltere.They are divided in to three regions namely
scabellum, pedicel and capitellum. They act as balancers. E.g. Hind wings housefly and
front wings, male stylopids, mosquito and male scale insect.
9. Pseudohalteres: They are short and modified in to pseudohalteres which are dumbbell
shaped. Eg: Front wings of Strepsiptera

37
ElytraHemelytraMembranous wings
Fringed wingsFissured wings Halteres
Tegmina wings Scaly wings

38
WING COUPLING APPARATUS/ORGANS/MECHNISMS
 Among the insects with two pairs of wings, the wings may work separately as in the
dragonflies and damselflies.
 For taking flight, insect need to keep both the fore and hind wings together as a single
unit. The structures in the form of lobes, bristles, hairs or spines that help the wings to
be together are known as wing coupling organs.
1. Jugate type or jugum type:
The costal margin of the front wing possess a small lobe at the base called
fibula which rest on the surface of the hind wing or sometimes engages with spines
present on the upper surface of hind wings . e.g.: primitive lepidopterans of the family
Hepialidae.
2. Frenulum/Franate/retinaculum type:
The hind wings possess bristle or spine like structure or group of hairs known
as frenulum.The forewings possess hook like retinaculum on anal side. During
flight the frenulum passes beneath the retinaculum and thus the both the wings are
kept together. e.g.: Fruit sucking moth.
3. Amplexiform:
Costal margin of hind wing and anal margin of forewing overlap one above
the other e.g.: butterfly
4. Hamuli/Hamulate :
TheSmall curved hook like structures present on the costal margin of the hind
wing known as Hamuli that fit into the upward fold of the anal margin of the
forewings.e.g.hymenopterans (wasps and bees)
Jugate typeFrenulum type
Amplexiform type Hamuli type

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SENSORY AND SOUND PRODUCING ORGANS
The sense organs in an insect body are distributed on different parts and respond to a
given stimulus such as light, sound, touch, chemicals etc.
The sense organs may be classified as;
1. Photoreceptors(or) Visual organs- To detect light energy.
2. Auditory receptors (or) organs of hearing- To detect sound waves.
3. Chemoreceptor’s which respond to chemicals- To detect smell and taste.
4. Mechanoreceptor/Tactile receptors which respond to touch- To detect mechanical force
5. Thermoreceptor – To detect heat.
1. Visual organs or photoreceptors:These are two types, Compound eyes and
Simple eyes.
I. Compound eyes:These organs possess the ability to perceive light energy and
able to produce a nerve impulse. The compound eyes may be completely absent in insects
like Protura or they may remain reduced in endoparasitic Hymenoptera. The compound eyes
are present on either side of the head capsule of an adult insect and also in the nymphs of
Exopterygota.
These are a pair and consist of number of individual units (or) facets called ommatidia.
Function is to gather light.
Classification of Compound eyes based on image formation;
 Apposition eyes:These are active during day time (diurnal insects);e.g.: butterflies
 Superposition eyes:These are active during evening and night time (Nocturnal
insects); e.g.: moths
II. Simple eyes (or) ocelli:These are of two types
 Dorsal ocelli:Seen in nymphs and adults of Hemimetabolous insects and adults of
Holometabola.Dorsal ocelli are represented by fenestrae in cockroach. It perceive
light to maintain diurnal rhythm.
 Lateral ocelli:Also known as stemmata. These are present on the lateral sides of
the head of Endopterygote larva. It helps to detect form, colour and movement.
2. Auditory organs (or) organs of hearing:
Insects are provided with structures (or) organs that are able to perceive the sound
waves (or) the aquatic water currents. Among the organs of hearing, the auditory hairs,
tympanal organ and Jhonston’s organ are important.

40
 Auditory hairs :
These are present on the body of insects such as larvae of Lepidoptera which are
developed from the modified epidermal cells. These respond to the sounds of air (or) water
currents mediated by the hair sensillae (or) trichoid
 Tympanal organ :
Tympanum is present one on either side of the 1st abdominal segment of short horned
grasshoppers, on the base of foretibia in long horned grasshoppers and crickets, and on thorax
or abdomen in Lepidoptera.
 Jhonston’s organ:
It is present on the pedicel of antennae and functions asan auditory organ responding
to air (or) water currents. They are absent in Collembola.
 Pilifer of hawk moths (sphingid moths):
A unique auditory organ, sensitive to ultrasonic frequencies is found in the head of
several species of Sphingidae.
3.Mechanoreceptor: (detect mechanical force)
 Trichoid sensilla:Hair like sense organ. Sense cell associated with spur and seta.
These cells are sensitive to touch and are located in antenna and mouthparts.
 Campaniform / Dome sensilla:These cells are sensitive to pressure and located in
legs joints and wing bases.
 Chordotonal organ:The specialized sensory organs that receive vibration are
subcuticular mechanoreceptors called chordotonal organ.
4.Chemoreceptors: (detect smell and taste):
It contains sensilla with one pore (uniporous) or more pores (multiporous).
♣ Uniporous chemoreceptors mostly detect chemicals of solid and liquid form
by contact called gustatory receptorsand located in antennae.
♣ Multiporous chemoreceptor’s detect chemicals in vapour form at distant by
smell called olfactory receptors and located in mouth and tarsi.
5. Thermoreceptor – (detect heat)
Present in poikilothermic insects and sensitive to temperature changes. E.g. Bed bugs.

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METAMORPHOSIS
 Metamorphosis is derived from Greek word ‘Meta’ = Change, ‘morph’ = form or
structure.
 Series of changes that takes place during the development of an insect from egg to
adult are collectively known as metamorphosis.
 Metamorphosis include three developmental processes namely, growth,
differentiation and reproduction which takes place in larval, pupal and adult
stages respectively.
o Eclosion: The process of hatching of eggs after fully development of embryo called
eclosion.
o Instar: It is the forms of the body during two inter moults. The larva is known as first
instar, immediately after hatching from egg, and as second instar after first moult and
so on
o Stadium: The interval or time period between two moults is known as stadium.
o Exuviae: The skin shed during moulting process is known as exuviae.
o Imago (or) Adult: It is the final stage of insect with well-developed organs for
reproduction, which emerges out from pupal body.
o Sub-imago: It is a pre adult stage with fully developed wings but without
reproductive organs .E.g.: mayflies (Ephemeroptera)
Types of metamorphosis:
1. Ametamorphosis (Ametabolous)
2. Incomplete metamorphosis (Hemimetabolous)
3.Gradual metamorphosis: (Paurometabola)
4. Complete metamorphosis/Holometabolous
5. Hyper metamorphosis
1. Ametamorphosis:
♠ E.g.: Apterygote e.g.: silver fish, springtails.
♠ Insects do not undergo any metamorphosis.
♠ These insects have only three stages in their life namely egg, young ones and
adult.
♠ The hatching insect resembles the adult in all respects except for the size and
called as juveniles.
♠ Moulting continues throughout the life

42
2. Hemimetabola: (Incomplete metamorphosis)
♠ E.g. Dragonfly, damselfly and may fly.
♠ These insects also have three stages in their life namely egg, naiads and
adult. Pupal stage is absent.
♠ The young ones are aquatic and are called as naiads.
♠ They are different from adults in habit and habitat.
♠ They breathe by means of tracheal gills.
♠ In dragonfly naiad the lower lip (labium) is called mask which is hinged and
provided with hooks for capturing prey. After final moult, the insects have
fully developed wings suited for aerial life.
3. Paurometabola: (Gradual metamorphosis)-
♠ E. g. grasshoppers, cockroaches, termites, true bugs, cicadas, and hoppers.
♠ It is also called as simple metamorphosis.
♠ The life cycle includes egg, nymph and adult stages.
♠ The nymph resembles the adult in all the characters except wings. Nymphs
possess wing buds which transform in to fully developed wings in adult stage.
♠ Both nymphs and adults share the same habitat.
♠ In these insects, wings develop externally and hence are also called as
Exopterygota.
♠ Pupal stage is absent hence, development is said to be direct and simple.
4. Complete or Holometamorphosis or indirect development:
♠ E.g. Butterfly, moth, Beetles, weevils, fly and bees.
♠ The life cycle includes four stages; egg, larva, pupa and adult.
♠ Larvae of butterflies are called caterpillar.
♠ Larva differs from the adult both in body structure and habits. Larva has both
thoracic and abdominal legs, sometimes legs may be absent in larva, whereas
adult has only thoracic legs.
♠ Compound eyes are absent in larva.
♠ Larva undergoes moulting to enter in to pupal stage from which the adult
insect emerges.
♠ Wings develop internally during the pupal stage and hence, they are called
Endoptreygotes.

43
5. Hypermetamorphosis:
♠ This is a peculiar type of development which consists of two or more types or
forms of larvae in the life cycle of insects.
♠ In majority of the cases the first larval, instar is campodeiform and the
subsequent larval forms depends on type and mode of life of the larva. E.g.: In
blister beetle (Meloidae; Coleoptera), the first larval instar is campodeiform
followed by scarabeiform larval type.
SIGNIFICANCE OF METAMORPHOSIS
i. It helps the insect to tide over unfavorable climate conditions by entering into
hibernation, aestivation and or diapauses.
ii. It helps the insect to accommodate growth by periodical shedding of their old cuticle
and by formation of new cuticle.
iii. It helps the insect to reduce or avoid competition for food amongst themselves by
either entering into inactive stage or by acquiring different feeding habits and habitats.
iv. It helps the insect as a protective adaptation by a way of mimicry. i.e. resembles to the
nature.
v. It also serves as an important aspect in classification of insects.
SEASONAL ADOPTIONS
 Diapause : -
 It is the period of arrested growth or development in the life cycle of the insects
during which the physiological processes like differentiation and reproduction are
suspended. Diapause is represented by low rate of metabolism, low O2 consumption,
low body weight, low body water content and vitamin deficiency in the blood.
Diapause may occur in egg, larva, nymph, pupa or adult stage.
 The occurrence of diapause during summer due to high temperatures is known as
“aestivation”
 Whereas the period of inactivity during winter due to low temperatures known as
“hibernation”.

44
IMMATURE STAGES OF INSECTS
 Immature stages of exopterygote insects are known as Nymphs and endopterygote
insects are known as Larvae.
Differences between Larva and Nymph
Sr.No. Larva Nymph
1. It is an immature stage, of Endopterygotes. Immature stage of exopterygotes
2. It undergoes holometamorphosis It undergoes hemimetamorphosis
3. Body is vermiform which differs from the adult
both in structure and feeding habits
Body resembles the adult in all the
characters except wings
4. Consists of ocelli and reduced Antennae Have compound eyes and antennae
5. Possess both thoracic and abdominal legs Possess only thoracic legs.
6. The larva is different from adult in feeding habits
and behaviour
Nymph resembles the adult in feeding
habits and behaviour
7. The larva enters pupal stage No pupal stage
8. E.g.: Lepidoptera, Coleoptera Hemiptera, Orthoptera.
TYPES OF LARVA
1. Protopod larva: E.g.: Endoparasitic Hymenoptera.
The larvae are partially developed. They possess well developed head and thoracic
segments but lack segmentation in the abdomen. They possess rudimentary cephalic and
thoracic appendages but no abdominal appendages. They have partially developed digestive
system and underdeveloped respiratory and nervous systems.
2. Oligopod larva:
Thoracic legs are well developed. Abdominal legs are absent. These are classified in
to two types’ viz., campodeiform and scarabaeiform.

45
Differences between Campodeiform and Scarabaeiform
Sr.
No.
Campodeiform Scarabaeiform
1 The body is long and fusiform in shape Body is ‘C’ shaped
2 Body is dorso-ventrally compressed with
sclerotized cuticle
Body is cylindrical or sub cylindrical,
stout and fleshy in nature
3 Prognathous type of head Hypognathous type of head
4 Long thoracic legs Short thoracic legs
5 Apair ofterminalabdominal processes (anal
cerci) are present
Absent
6 These are active Inactive
7 Predatory in nature Phytophagous
8 e.g. grub of antlion /grub of lady bird beetle. e.g.: grub of rhinoceros beetle/white grub
3. Polypod larva (Eruciform larva):
The larva possess well defined segmentation of the body with three pairs of thoracic
legs, 2-5 pairs of abdominal legs (3rd, 4th, 5th, 6th and 10th abdominal segment. They are
phytophagous and destructive.
Different types of polypod larvae:
A. Hairy caterpillar larval body is fully covered with hairsE.g.: Red hairy caterpillar, Castor
hairy caterpillar
B. Sphingid caterpillar / larva the larva consists of a horn (or) hook on the dorsal surface of
8th abdominal segment. E.g.: Gingelly death’s head moth
C. Looper: Only two pairs of abdominal legs present on 6th and last abdominal segment
during walking the insect body forms a complete loop like structure hence, the name
looper.E.g.: Mango looper.
D. Semilooper: e.g.: Castor semilooper First two pairs of abdominal legs (on 3 rd and 4 th
segments) are reduced, hence a part of the insect body forms a small loop during its
movementE.g.:Castor semilooper.
4. Apodous larva:
These are characterized by the absence of trunk appendages (or) legs. They possess 3
pairs of sensory papillae in the place of thoracic legs. They are usually derived from
Oligopod type.Based on the degree of development of the head capsule and its appendages,
these larvas are divided in to 3 types.

46
a. Eucephalous: e.g.: Sub order Nematocera of Diptera, Mosquito(Culcidae) The larva
consists of a well sclerotized head capsule.
b.Hemicephalous. e.g.: Brachycera of Diptera, robberflies (Asilidae) Larva possess partially
developed head capsule
c. Acephalous e.g.: Cyclorrhapa of Diptera, Muscidae (houseflies)the larva are characterized
by the absence of head capsule and mouth parts are represented by mouth hooks.
Appearance Larval Type Common
Name
Description Examples
Eruciform Caterpillar
Body cylindrical with
short thoracic legs
and 2-10 pairs of
fleshy abdominal
prolegs
Moths
and
butterflies
Campodeiform Crawler
Elongated, flattened
body with prominent
antennae and/or
cerci. Thoracic legs
adapted for running
Lady
beetle,
lacewing
Scarabaeiform
White
grub
Body robust and "C"-
shaped with no
abdominal prolegs
and short thoracic
legs
June
beetle,
dung
beetle
Elateriform Wireworm
Body long, smooth,
and cylindrical with
hard exoskeleton and
very short thoracic
legs
Click
beetle,
Flour
beetle
Vermiform Maggot
Body fleshy, worm-
like. No head capsule
or walking legs
House fly,
flesh fly

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TYPES OF PUPA
It is resting, inactive stage of the holometabolous insects and transitional phase
during which the wings are developed and the insect attain matured sexual organs. The pupa
is incapable of feeding, locomotion except in some cases where they crawl (Neuroptera)
(Aphid lion), e.g.: mosquitoes. Later it emerges as adult, pupation may be takes place either
in soil, or on the plant surface or within the webs.
Pupae are divided on the following bases;
I. Based on the presence or absence of powerful mandibles
Decticous pupae Adecticous pupae
Possess relatively powerful mandibles which
are used for escaping of the adult from the
cocoon i.e. to break the cocoon. e.g.:
Neuroptera
Do not possess the mandibles but with the
help of other appendages, adults escape from
the cocoon e.g.: Lepidoptera, Diptera.
II. Based on the attachment on the appendages (or) shape of the pupae
1. Exarate pupa: e.g.:Coleoptera
The pupae have appendages which are free without any secondary attachment to the
body
2. Obtect pupa eg: Lepidoptera (moths)
The pupae have appendages which are firmly pressed against the body and the pupa is
highly chitinized.
3. Coarctate: e.g.: Diptera (housefly)
The pupa remains enclosed in a puparium formed by the last larval skin and the pupa
looks like a capsule or barrel.
4. Chrysalis: eg: butterflies
It is an obtect type of pupa which has golden colouration and a stalk.

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Appearance Pupal
Type
Common
Name
Description Examples
Obtect None
Developing appendages
(antennae, wings, legs,
etc.) held tightly against
the body by a shell-like
casing. Often found
enclosed within a silken
cocoon.
Butterflies
and moths
Exarate None
All developing
appendages free and
visible externally
Beetles,
Lacewings
Coarctate Puparium
Body encased within the
hard exoskeleton of the
next-to-last larval instar
housefly
Chrysalis None
It is an obtect type of
pupa which has golden
colouration and a stalk.
butterflies

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STUDY OF INSECT DIGESTIVE SYSTEM
 Digestive system of insect consists of Alimentary canal and Salivary glands.
 Alimentary canal: It is a long, muscular and tubular structure. The
alimentary canal in insects extends from mouth to anus which is divided in to three
parts, foregut, midgut and hindgut.
1. Foregut (stomodaeum):
 Ectodermal in origin.
 Ectodermic Cells secretes cuticular layer called Intima.
 It is the anterior part of the alimentary canal which starts with the mouth cavity and
ends with the gizzard (or) proventriculus.
 Terminal mouthparts lead into a preoralcavity. Preoralcavity between epipharynx and
hypopharynx is called asCibarium. Preoralcavity between hypopharynx and salivary
duct is Salivarium.
 It is divided in to pharynx,esophagus, crop and gizzard.
i. Pharynx: Behind the mouth a well musculated organ called Pharynx is
present which pushes the food into esophagus. Pharynx also acts as a sucking
pump in sap feeders. It is the region between the mouth and oesophagus.It
concerned with ingestion and back word flow of food.
ii. Esophagus: It is a narrow Simple tube of the foregut through which the foods
get transported from pharynx into the crop.
iii. Crop: It is a sac like structure which is a dilated form and mainly serves the
purpose of storage of food material. In honey bees crop is called as honey
stomach where nectar conversion occurs.
iv. Gizzard (Proventriculus): It formsthe last portion of foregut. This consists of
the cuticular intima layer modified in to teeth like denticles that help for
grinding the food material.It is found in solid feeders and absent in
fluidfeeders or sap feeders.

50
 Stomodeal valve or cardiac valve:
 After gizzard the foregut forms into a stomodeal valve or cardiac valve
which is surrounded by gastric (or) hepatic caecae.
 This prevents backward movement of food. Foregut opens in to midgut
through stomodael / cardiac valve.
Proventriculus
2. Midgut (Ventriculus or mesenteron or stomach),(Middle)
 Endodermal in origin.Is concern with;
i.Secretion of Enzymes,ii.Digestion of food, iii.Absorption of food.
 An endodermic cell does not secrete intima but instead of that secretes delicate
membrane called Peritrophic membrane.
 Midgut consists of an inner delicate layer called peritrophic membrane secreted by
the epithelial cells. The peritrophic membrane protects the tender epithelial cells of
the midgut from abrasion by hard food particles. Present in solid feeders and absent
in sap feeders.
 The midgut is a long tube it carries eight small blunt tubes known as gastric or
hepatic or enteric caeca. It increase the surface area of malpighian tubules and they
are secretary and absorptive in function.
 Filter chamber:
 This is a characteristic arrangement of the midgut in hemipteran insects (fluid
feeders).
 This is closely bound to either posterior part of midgut or the anterior hindgut
and Malpighian tubules.
 Filter chamber enables the excess fluids including sugar in the food to pass
directly from the anterior part of the midgut to the hindgut without passing
through the middle portion of midgut thus preventing excessive dilution of
haemolymph, enzymes and facilitate better enzyme activity.

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Filter chamber
 Pyloric valve or proctodeal valve: Present between midgut and hingut, which
regulate food flow.
3. Hindgut (Proctodaeum) (Posterior)
 Ectodermal in origin.Intima present.
 In termites, digestion takes place in colon of hindgutwhich secretes the enzyme
cellulase for digest the wood material rich in cellulose.
 Anterior end of the hindgut can be marked by the presence of a set of malpighian
tubules which are excretory in function.
 Hindgut is divided into 3 regions namely ileum, colon and rectum.
i. Ileum is a small intestine (or) tube like structure.
ii. Colon is a large intestine.
iii. Rectum - The rectum may sometimes get differentiated into rectal
papillae (or) pads which vary in number from 3-6. These are involved in
reabsorption of water, salts from the faecal (waste) matter.
 Salivary glands:-
 These are a pair of glands involved in the secretion of salivary juices.
 These glands present either sides of esophagus which open at the base of the
hypopharynx through small salivary ducts.
 In case of silkworm (or) lepidopteran larvae, the salivary glands produce silk
and anti-coagulants in blood suckers like mosquitoes.
 Digestive enzymessuch as;
♠ Amylases–Helps for digestion of Starch.
♠ Lipases -Helps for digestion of Fats & Lipids.
♠ Proteases–Helps for digestion of Protein.
♠ Invertase – Helps for digestion of Sucrose.(Present in honey bees)
♠ Maltase - Helps for digestion of Maltose.
♠ Cellulase -Helps for digestion of Cellulose.(Present in termites)

52
STUDY OF INSECT NERVOUS SYSTEM
 The nervous system functions as a link between the sense organs which respond to
various external and internal stimuli and the effectors organs such as muscles,
glands
 The sense organs include the structures with various sensilla that respond to sounds,
weather factors, smell etc.
 Nervous system consists of elongated cells which form the physiologically functional
elements that are known as neurons. These neurons carry the information in the form
of electrical impulses. It is a unit of nervous system.
STRUCTURE OF A NEURON
 The nerve cells are called neurons which are derived from ectoderm.
 Each neuron consists of a prominent nucleated cell body known as perikaryon (or)
soma and an elongated cytoplasmic thin fibre called the ‘axon’ extends to make
contact with other neurons or with effector organs, the muscles and group of small
branches called the ‘dendrites’.
 The axon gives lateral branches called collaterals. Both the axon and collaterals end
in fine fibrils known as terminal arborizations.
 The neurons get connected with each other by having a link between the terminal
arborizations of the axon of one neuron and dendrites of the soma of other neuron
through a ‘synapse’.

53
Classification of neurons:
I. Based on their structure:
1. Unipolar / monopolar:Have a single axon without collaterals and dendrites.
2. Bipolar:Have either collaterals or dendrites in addition to axon.
3. Multipolar:Neurons have an axon with several collaterals and dendrites
II. Based on function: 3 kinds of neurons.
1. Sensory / afferent:Present just beneath the integument and associated with sensory
organs. Carry impulses from sense organs to the central nervous system.
2. Motor / efferent neurons:Always unipolar / monopolar.Carry impulses from
central nervous system to the organs.
3. Association / internuntial neurons:Associated in between sensory and motor
neurons.
 The point at which neurons receive information from or convey to another neuron is
known as synapse. Synaptic gap is approximately 100 0
A (20-25nm).
Nervous system can be grouped in to three;
1. Central nervous system (CNS)
2. Visceral or sympathetic nervous system
3. Peripheral nervous system

54
1. CENTRAL NERVOUS SYSTEM (CNS)
 Insect have a decentralized nervous system.
 The group of nerve cells or neurons is called ganglion.
 CNS consists of double series of ganglia joined together by longitudinal and
transverse fibers.
 Generally each body segment possesses a pair of ganglia, so closely united as they
appear to be one.
 The ganglia of adjoining segments are joined together by longitudinal fibers called
as connectives.
 The ganglia of same segment unite by transverse fibers called as commissures.
 CNS consists of brain(supraoesophageal/cerebral ganglion), sub-
oesophagealganglion and ventral nervecord.

55
Brain (Supra-oesophageal ganglion):
 It is present in the head above the oesophagus in the head. It is formed by the union of
the ganglia of first 3 segments of the head. Brain is divided into protocerebrum,
deutocerebrum and tritocerebrum.
 Protocerebrum:
 It is also known as fore-brain. It is formed by the union of the ganglia of pre-
antennarysegment and forms the greater part of the brain. It gives nerve
connection to the compound eyes and ocelli. It is bilobed and continuous laterally
with the optic lobes.
 Deutocerebrum:
 It is also known as mid-brain. It is formed from the ganglia of antennary segment
and it gives nerve connection to the antenna.
 Tritocerebrum :
 It is also known as hind brain. It is formed by the union of ganglia of
intercalarysegment and is relatively small. It gives nerves to the labrum.
Sub-oesophageal ganglion:
 It is present in the head below the oesophagus in the head. It is formed by the union of
ganglia of the gnathocephalic segments. It gives nerves to mandibular, maxillary,
labialsegment, salivaryducts, part of cervical muscles in the neck region and
corpora allata.
Ventral Nerve Cord (VNC):
 Ventral nerve card consists of a chain of segmented ganglia connected by means of
longitudinal connectives and transverse commissures.
 In thorax, there are 3 ganglia. It controls the locomotory organs and gives nerve
connection to the legs and wings called thoracic ganglia.
 In abdomen, there are about 8 ganglia. Each ganglion gives off nerves to respective
segments.

56
Mechanism of impulse conduction
 Conduction of nerve impulse is mainly of two types-
1. Axonic- Electrical conduction through Na and K ionic movement
2. Synaptic- Bio-Chemical transmission (Acetylcholine production)
 In axonic conduction ionic composition varies between inside and outside of axon
resulting in excitable conditions, which leads to impulse conduction as electrical
response.
 In synaptic conduction neurochemical transmitters are involved in the impulse
conduction through the synaptic gap. Neurotransmitters and the type of reactions
helping in the impulse conduction are as follows.
Acetyl CO-A + Choline chlorideAcetylaseAcetyl choline
Acetyl Choline Esterase
Acetyl choline Choline + Acetic acid

57
REPRODUCTION IN INSECTS
 The reproductive system is divided in to two parts namely, internal genitalia and
external genitalia.
 The internal genitalia serve to the development of germ cells. The external genitalia
accomplish the union of two sexes and enable the female to deposit eggs.
Female reproductive system
 The main functions of the female reproductive system are egg production and storage
of male's spermatozoa until the eggs are ready to be fertilized.
It consists of;
 A pair of ovaries which possess number of ovarioles,
 A pair of oviducts,
 A common oviduct / Median oviduct ,
 spermatheca ,
 A pair of accessory glands and
 Bursa copulatrix/copulatory pouch/genital chamber/vagina
1. Ovaries :
 These are the prominent visceral organs present on the either side of alimentary canal.
 These are paired in structured mainly covered with fat body and trachea.
 Each ovary consists of eight ovarioles or egg tubes. It consists of 3 parts namely;
Terminal filament, Egg tube, Pedicel.
 The functions of ovary are production of eggs or ova and storage of male's
spermatozoa.

58
Types of ovarioles:-
 Based on the presence or absence of nutritive cells and their location ovarioles are
categorized in to two;
i. Panoistic - In these, the nutritive cells are absent. e.g.: Odonata, Dictyoptera,
Orthoptera and Ephemeroptera
ii. Meriostic - They contain trophocytes / nutritive cells which vary in their
position. Based on the position of trophocytes Meriostic ovarioles are
classified into;
 Polytrophic - e.g.: Mecoptera, Dermaptera, Psocoptera
 Acrotrophic (Teletrophic) - e.g.: Hemiptera and Coleoptera
2. Lateral oviducts: Proximal end of the ovarioles of each ovary join to form a lateral
oviduct on each side. Function is to transfer the eggs form ovary to the median oviduct.
3. Median Oviduct: Two lateral oviducts combine to form a median oviduct.
4. Vagina: (genital chamber) Median duct opens in to a tubular genital chamber or vagina
formed by invagination of body wall from VIII segment.
5. Bursa Copulatrix:
 In some insects the genital chamber or vagina develops a separate pouch called Bursa
Copulatrix in to which insects have two reproductive openings
 One is vulva for receiving the sperms open on VIII sternum and another one is
ovipore or gonopore on IX segment for discharging eggs. E.g.: Lepidoptera and
water beetles.
6. Spermatheca:
 It is a sac like structure consisting of a spermathecal gland and opens in to vagina
through spermathecal duct.
 This is mainly used for temporary storage of sperms.
 It also produces some fluids responsible for longevity of sperms cells for several
hours.
7. Accessory glands: (collateral glands)
 These are a pair structured which open in to the distal portion of vagina.
 They secrete the sticky substance responsible for the formation of ootheca of
cockroach, preying mantid and poisonous secretions in case of Hymenoptera.
 These sticky substances are useful for attachment of egg to the substrate on which
they are laid.

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 Oogenesis-The process in which primary oocyte developed in to fully developed ova
is called oogenesis.
Difference between male and female reproductive system
Male reproductive system Female reproductive system
A pair of testes composed of follicles or
sperm tubes.
A pair of ovaries which possess number of
ovarioles.
A pair of vasa deferens. A pair of oviducts.
Seminal vesicle. A common oviduct / Median oviduct.
Ejaculatory duct. A spermatheca.
Accessory glands. A pair of accessory glands.
Genitalia. (aedeagus or penis) Bursa copulatrix/copulatrix pouch/genital
chamber/vagina.
Male reproductive system
 The main functions of the male reproductive system are the production and storage of
spermatozoa and their transport in a viable state to the reproductive tract of the
female.
A male reproductive organ consists of;
 A pair of testes composed of follicles or sperm tubes
 A pair of vasa deferens,
 seminal vesicle
 ejaculatory duct
 accessory glands
 Genitalia.

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1. Testes:
 These are paired in structured &lie in visceral cavity above the alimentary canal.
 Each testes are well supplied with trachea and fat body tissues.
 Each testis consists of number of oval shaped structures known as follicles or sperm
tubes. Each follicle has a layer of epithelial cells.
 The entire follicle is covered by a peritoneal membrane whereas the testes are
completely enveloped within a coat known as scrotum.
 The functions of testes are production and storage of spermatozoa.
2. Vasa differentia:
 These are the long tubes formed by the union of vasa efferens which receives the
sperms from testis and allow their transport to the ejaculatory duct.
3. Seminal vesicles:
 Each vasa deferens becomes enlarged posteriorly to form a sac like structure called
seminal vesicle for storage of spermatozoa for some time.
4. Ejaculatory duct:
 Both the vasa deferens of the two testes unites posteriorly to form a common median
ejaculatory duct.
 The terminal section of ejaculatory duct is enclosed in a finger like invagination of
body wall called male copulatory organ or aedeagus or penis.
 The function of aedeagus is that ejaculate the spermatozoa into the female genital
tract.

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5. Accessory glands:
 These are 1-3 pairs of glands which open in to the ejaculatory duct
 In most cases their secretion mix with spermatozoa. These glands are called
mushroom glands in cockroaches and mantid because of their appearance as
mushrooms.
 This secretion facilitates sperm transmission from male to female.
Types of Reproduction
1. Oviparity:
 Insects reproduce by laying eggs by the female which later hatch and produce the
young ones. e.g.: moths and butterflies. (Higher order insect)
2. Viviparity:
 It is the phenomenon of reproduction where the female gives birth to the young ones
instead of laying eggs.Viviparity is classified in to 4 types.
i) Ovo-viviparity:
 Insects retain the eggs within the genital track until the eggs are ready to hatch (or)
giving birth to young ones. e.g.: Thysanoptera (Thrips)
(ii) Adenoparous viviparity:
 It is a type of viviparity where the eggs have sufficient yolk, complete their
embryonic development and retain in the uterus. Eggs hatch and the young ones get
nourishment from special nourishment glands called milk glands.
(iii) Pseudoplacental viviparity:
 It is a phenomenon where insect have eggs with little (or) no yolk. Hatching takes
place within the mother and the nourishment for the young one is received through
embryonic maternal structure called pseudoplacenta e.g.: Psocoptera, Dermaptera,
aphids etc.

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(iv) Haemocoelous viviparity:
 It is a type of reproduction where the eggs are retained within the haemocoel and the
embryonic development as well as the nourishment of young one takes place through
the transfer of nutrients from the haemolymph of mother. e.g: strepsipterans & some
larvae of cecidomyids (Diptera).
3. Parthenogenesis:
 It is the ability of the females to reproduce without fertilization / copulation with
males. This usually occurs due to the genetic characters, due to heredity, failure in
finding a mate, hormonal changes within the body and weather factors. . e.g.: aphids.
4. Paedogenesis (or) Neoteny:
 It is a phenomenon where the immature insects or stages give birth to young ones.
This usually occurs due to the hormonal imbalance. Most of the insects which
reproduce by paedogenesis also reproduce by parthenogenesis. e.g.: cecidomyids.
(Mustad sawfly).
5. Polyembryony:
 It is a type of reproduction where insects reproduce by giving birth to two or more
young ones instead of a single one, as two or more embryos are produced from a
single egg. e.g.: endoparasitic Hymenoptera like platygaster.
6. Hermaphroditism:
 It is a type of reproduction where both male and female gonads are present in the
same individual. It may be a functional hermaphroditism as in case of Icerya
purchsi (scale insect)(or) nonfunctional as in case of stonefly, Perla marginata.
7. Castration:
 It is a type of reproduction where the separation of the individuals occurs mainly due
to the development of the reproductive organs. The insects with well-developed
ovaries develop in to females (queens), the insects with well-developed testis develop
in to males (drones) and insects with underdeveloped ovaries develop in to workers.
e.g.: social insects such as honey bees.

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STUDY OF INSECT RESPIRATORY SYSTEM
 It is also called as tracheal system.
 In insects, exchange of gases takes place through tubular structures, called trachea.
 They are distributed throughout the body collectively forming tracheal system.
 These trachea open outside on the body wall through small openings called spiracles.
 Spiracles occur on the pleural surfaces of the body, one on either side of each
segment.
 The tracheas are divided into very fine branches known as tracheoles. They supply
oxygen to the body tissues. These tracheoles are formed in to cells called
‘tracheoblast’
 The tracheal system with functional spiracles is called the open tracheal system and
with non-functional spiracles is called closed tracheal system.
 Tracheas are fine elastic tubular structures which are ectodermal in origin.
 A spiral thickening throughout the length of the tube of trachea. These spiral
thickenings are known as ‘taenidia’ which give support to the trachea without being
collapsed when there is no air.

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Structure of trachea
Differences between trachea and tracheoles
Trachea Tracheoles
These arelargetubesrunningfrom spiracles. Fine tubes arising distally from trachea.
Taenidia present. Absent.
Intima layer isshedduringmoulting. Intima layer is retained,
unchangedduringmoulting.
Never become intracellular. Intracellular.
Theintimalayerconsistsofprotein–
chitinmatrixwithresilin.
Chitin– protein matrix present,
resilinabsent.
Tracheal trunks:
 The trachea coming from spiracles throughout the body join with those of
neighboring spiracles forming ‘longitudinal trunks’. Likewise, these tracheas by
combining with those coming from dorsal, lateral and ventral sides of the body fuse
to form transverse commissures and longitudinal connectives.
 All these in total form into dorsal trunk, lateral trunks which are two in number
and one ventral trunk.
 The dorsal trunk supply oxygen to proximal part of the body as well as to heart
whereas the ventral supplies to then central nervous system. The two lateral
longitudinal trunks spread tracheoles to alimentary canal, legs, gonads and wings.

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 Head do not contain spiracles, air is supplied through the first pair spiracles by
means of two main branches of the dorsal longitudinal trunk, where one branch
supply O2 to eyes, antenna, brain; other branch to mouthparts and muscles of the
head.
Tracheal system (dorsal tracheal trunks)
Spiracles:
 They are the openings of the internal tubular trachea.
 Except in Diplura, in all the orders, spiracles are absent in prothorax and
distributed in meso, metathorax and abdomen.
 A total of 10pairs are present in general, 2 pairs in thorax and 8 pairs in abdomen.
 Spiracles are situated on pleural surface. They consist of a small ring like sclerite at
opening called ‘peritreme’ leading to a cavity known as atrium.
 The closing and opening of spiracles is accompanied by atrial valve lined with
fibrous processes and form so called felt chamber which reduces water loss in the
absence of closing mechanism.

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Structure of spiracle
 Classification of tracheal system based on number and arrangement of
functional spiracles: (Types of respiration).
1. Holopneustic:
These are primitive type with 2 pairs of spiracles on thorax and 8 pairs on
abdomen. All the spiracles are functional. 1 + 1 + 8.
E.g. dragonflies, grasshoppers and cockroach.
2. Hemipneustic:
One or more pairs of spiracles become non-functional. They are;
a) Peripneustic: Metathoracic spiracle is closed. 1+ 0 + 8.
e.g.: larvae of Lepidoptera, Hymenoptera, Coleoptera.
b) Amphipneustic: only mesothoracic and last pair of abdominal spiracles is open. 1 + 0 + 1.
e.g: larva of cyclorrhaphan Diptera.
c) Propneustic: Only one pair i.e. mesothoracic spiracles are open,
1 + 0 +0 e.g.: mosquito pupa.
d) Metapneustic: only last pair of abdominal spiracles is open.
0 + 0 + 1. e.g.: mosquito larvae.
e) Apneustic: No functional spiracles. e.g: mayfly larva, nymph of Odonata
3. Hypopneustic:
1 or 2 pairs of spiracles may completely disappear or absent
e.g.: Siphunculata, Mallophaga
4. Hyperpneustic:
More than 10 pairs of spiracles are present e.g.: Japyx sps. (dipluran)

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STUDY OF INSECT CIRCULATORY SYSTEM
 There are two types of circulatory systems in the animal kingdom.
 In many animals, the blood travels through vessels like arteries, capillaries and
veins. This is known as closed type of circulatory system.
 In insects the blood flows through the body cavity (i.e, heamocoel) irrigating various
tissues and organs. It is known as open type of circulatory system.
Haemocoel:
 Haemocoel of the insects is divided into 3sinuses(or) regions due to the presence of
two fibro muscular septa (or) diaphragms composed of connective tissues.
 Dorsal or Pericardial Sinus:
 The area lying in between the tergum and dorsal diaphragm.
 It contains heart.
 Ventral or Perineural Sinus:
 The area lying in between the sternum and ventral diaphragm.
 It contains nerve cord.
 Visceral Sinus:
 The area in between dorsal and ventral diaphragms.
 It harbour the visceral organs like alimentary canal and gonads.

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Main sinuses of haemocoel
Dorsal blood vessel:
 It is the principal blood conducting organ in insects which remain closed at
the posterior end and opens anteriorly in to the head.
 It is divided into an anterior aorta and posterior heart
1. Aorta:
 It is the anterior part of the dorsal blood vessel.
 Its functions as principal artery.
 It is present in the thoracic region and opens in to the head near the brain.
 Its attachment with the heart posteriorly is marked by an aortic valve.
2. Heart:
 It is the posterior part of dorsal blood vessel extending up to the terminal end of the
abdomen.
 Heart remains in position with the help of alary muscles. These alary muscles appear
to be distributed fan like over the heart.
 Heart consists of number of chambers marked by constrictions and the presence of
the opening called ‘ostia’ which allow the entry of blood from pericardial sinus in
to the heart.
 The number of Ostia depends upon the number of heart chambers which will be
usually 9.
 Heart mainly functions as the pumping organ in to the aorta.
Accessory pulsatile organs:

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 An insect consists of sac like structures called accessory pulsatile organs, which are
present at the base of the appendages such as wings, legs and antenna. They pulsate
independently and supply adequate blood to the appendages.
Circulatory system
Process of blood circulation:
 Heart mainly function as a pulsatile organ whose expansion and contraction leads to
blood circulation.
 It takes place generally in an anti-clock manner starting from posterior end to the
anterior end in a forward direction.
 Circulation of blood takes place in two phases due to the action of the alary muscles
as well as the muscles of the walls of the heart.
The two phases are;
1. Diastole: During which expansion of heart takes place.
2. Systole: Contraction of heart takes place.
1. Diastole:
 Expansion of heart (diastole) occurs, when the alary muscles that are spread fan like
over the heart and connected to the tergum get contracted.
 It results in increase of volume of heart and decrease in the area of pericardial
sinus.
 This creates a pressureon the blood in pericardial sinus forcing the blood to enter
into the heart through the Ostia.

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 These ostia allow only the entry of blood from the sinus in to the heart and prevent its
backflow from the heart to the sinus.
2. Systole:
 Contraction of heart (systole) is brought about by the expansion of the alary
muscles as well as contraction of the muscles of the heart wall.
 This creates pressure on the blood within the heart leading to its forward movement in
to the aorta.
 From the aorta blood enters in to the head and flows back bathing the visceral organs
in the visceral sinus and neural cord in the perineural sinus.
 The short period of rest between diastole and systole called as diastasis.
 The rate of heart beat generally varies with the body temperature and physiological
conditions of the body which in turn differs between species (or) between stages of
the insects.
Properties of blood:
1. Blood is colourless (or) green (or) yellowish with different types of haemocytes and
plasma. Green colour is due to chlorophyll dissolved in the plasma and red colour is
due to haemoglobin.
2. Blood covers up 5 – 40% of the total body weight that vary with the sex and stage
(or) age of the insect.
3. Insect blood contains proteins, lipids, sugars, organic acids, phosphates, pigments,
uric acid etc.
4. The insect blood of phytophagous insect is rich in ‘K’ where as that of carnivores is
rich in ‘Na’.
5. Specific gravity of the blood varies from 1.01 to 1.06.
6. pH
of the blood generally varies from 6 to 7.
7. The blood sugar of insects is trehalose.
8. Blood lacks vitamin ‘K’
Functions of blood:-
1. Transport of minerals or food materials:blood transports minerals, digested
products, hormones to different parts of the body.
2. Water storage:Blood stores water for the tissues.
3. Helps for moulting:Blood helps during the process of moulting for splitting up of the
old cuticle.

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4. Encapsulation: To protect from the large metazoan parasites, the haemocytes of
blood, become aggregated around the foreign body forming a capsule of 2-3 layers.
This leads to the death of the foreign bodies due to lack of O2 supply.
5. Phagocytosis: To get protection from microorganisms like bacteria, viruses and
fungi, the haemocytes completely engulf the foreign body and gets autolyzed.(This is
the principal function of haemocytes).
6. Immunity: Blood gives immunity by producing antibodies to restrict further
infections.
7. Connective tissue formation: Blood provides lipoproteins that are necessary for the
formation of the connective tissue.
8. Wound healing (or) coagulation :Haemocytes extend pseudopodia which forms a
cellular network over the wounded site (or) plasmtocytes coagulate forming a plug
over the wound (or) haemocytes are arranged in to multi layered sheaths over the
wounded site, thus helping in wound healing.
9. Detoxification: As the haemocytes are capable of detoxifying the toxic chemicals,
insects get the ability to resist the toxic effects of chemicals.
10. Reflex bleeding: It is a phenomenon where emission of blood occurs through the
pores (or) slits of the cuticle which mainly helps the insects for getting protection
from their natural enemies.
STUDY OF INSECT EXCRETORY SYSTEM
 What is excretion?
“It is simply removal of the unwanted metabolic end products or some of the nutrients
in excess form out of the body.”
 Why it is necessary?
 A constant maintenance of level of salt and water and also osmotic pressure in the
hemolymph.
 The organs of insect body, involved in the elimination of excess or unwanted
materials either toxic or not useful, are together known as excretory system.
The organs that are involved in the process of excretion are;
1.Malpighian tubules
2. Integument or body wall
3. Tracheal system
4. Alimentary canal
5. Nephrocytes

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6. Urate cells
7. Oenocytes
8. Labial glands and
9. Chloride cells
1. Malpighian tubules:
 These are discovered by an Italian scientist, Marcello Malpighi in the year 1669,
which were named after him by Heckel in 1820.
 The Malpighian tubules long, tubular structures which open proximally in between
midgut and hindgut and closed distally, floating freely in the haemolymph.
 Malpighian tubules vary in their shape and size. They may be simple or branched.
Their number varies from 2-250 (2 in scale insect and 250 in locust, 60 in
cockroach, 6 in moths and butterfly, 4 in bugs ).
 Malpighian tubulesare absent in aphids and Collembola.
 In some of the insects such as caterpillars and coleopterans(Beetles & Weevils), the
distal ends of the Malpighian tubules get reattached to the alimentary canal by
opening in to the rectum of hindgut. This condition is called ‘cryptonephridial
condition’. Thecryptonephridial arrangement is concerned with reabsorption of water
from rectum.

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Functions of Malpighian tubules:
1. This is the main organ of excretion and osmoregulation. It involved in regulation of salt,
water and nitrogenous waste material.
2. Helps in the process of excretion or removal of waste products in order to regulate the
internal body environment by maintaining ionic and water balance.
3. In case of glow worms (Fireflies), the distal ends of tubules produces light energy.
4. It also helps in the storage of Ca necessary for the processes such as hardening of
puparium.
5. In case of aphid lion the secretions of the tubules produce stalked eggs.
6. In case of spittle bugs spittle around the immature stages is also a Malpighian secretion.
2. Integument:
 Through the process of moulting, insects remove the waste nitrogenous products, i.e.
they are deposited in the form of exuviae.
 In some insects, where respiration occurs through body wall, CO2 is removed through
integument as waste product (cutaneous respiration).
3. Tracheal system:
 The respiratory tubes, the trachea which are distributed throughout the body, function
in elimination of CO2 through spiracles.
4. Rectum:
 Rectum plays an important role in excretion by reabsorbing the water from faeces.
Accessory organs of excretion-
5. Nephrocytes:
 These are the special cells that sieve the haemolymph and are distributed in the body
cavity.
 Nephrocytes are cells that take up foreign chemicals of relatively high molecular
weight which Malpighian tubules may be incapable of dealing with.
6. Oenocytes:
 These are large cells and are usually present near the abdominal spiracles. These are
the specialized cells of haemocoel involve in excretion.
7. Urate cells: (Fat bodies)

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 In some of the insects body cells which store urea or uric acid in the form of granules
are known as urate cells.
 Preserved uric acid can be utilized subsequently.
 These are present when Malpighian tubules are absent or may become nonfunctional.
 In some of the insects such as cockroach, the waste material in the form of urea or
uric acid is stored throughout its life in the fat body cells without any harmful effect.
This phenomenon of storage of urea / uric acid in the fat body cells is called ‘storage
excretion’ which is useful for supply of nitrogen, when insect feeds on nitrogen
deficient food.
8. Labial glands:
 These are seen in Collembola, Diplura, Thysanura. They consists of a sac like
structures called ampulla that leads to a long coiled that open at the base of labium in
the head. This gland helps to remove ammonia.
9. Chloride cells:
 These are the cells distributed on the body of aquatic insects such as larva ofmayfly
or stone fly. They absorb ions from salt water (body) and then excrete in to
surrounding medium to compensate the changes in the ionic concentration of
haemolymph.
STUDY OF INSECT ENDOCRINE SYSTEM
There are two types of secretrory structures occur in insect.
1.) Exocrine glands:
 It is a ducted glands and discharge their secretions outside the body.
 E.g. Wax glands, Lac glands, Mandibular glands, Maxillary glands, Labial glands,
Silk glands, Repugnatorial glands, Attractant glands and Poison glands.
2.) Endocrine glands:
 It is a ductless glands and their secretion (harmones) usually diffusing into the blood
which transports them to all parts of the body.
 Insect endocrine system is structurally and functionally integrated with nervous
system. It is also called as secretory system.
 They secrete harmones which travel in the blood to various organs of the body
coordinating their long term activities.
 Endocrine organs are of two types,
 1. Neuro-secretory cells in the central nervous system.
 2.Specialized endocrine glands such as
i) Corpora cardiaca

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ii) Corpora allata
iii) Prothoracic glands
iv) Weismann’s Ring:
1. Neurosecretory cells:
 These are typical neurons with secretory activity.
 They produce harmones which act directly on effector organs which in turn are
stimulated to secrete harmones.
 They occur in the mid region of brain and central nervous system.
 The secretions of neurosecretory cells are called brain hormone or activator
hormones.
 Large number of neurosecretory cellsmay be present in the nervous system and are
threetypes.a) Median NSC of the brain (PTTH harmone), b) Lateral NSC of the brain:
- They Stimulate protein synthesis, control water loss and Oocyte development and
activity. And c) Ventral NSC of the other ganglia (ventral nerve cord):
 These secretions are known to concern with activity, water regulation.
2. Corpora cardiaca:
 They are paired structures, lying in close association with neurosecretory cells of
brain.
 Each corpus cardiacum is transversed by neurosecretory axons from the brain.
Neurosecretions from brain, on reaching corpus cardiacum, is stored and periodically
released into the blood.
3. Corpora allata:
 They are glandular bodies, usually situated one on either side of the Oesophagous.
 Under the influence of brain hormone, corpora allata secretes Juvenile hormone
(JH) or neotenin which regulates metamorphosis or yolk deposition on eggs in
insect.
 JH helps to keep the insect in young stage only.
 It is also called as Juvenile hormone (JH) or neotenin.
4. Prothoracic glands:
 It is also known as ecdysial glands.
 They are twoin number and placed mostly in prothoracic region.

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 Prothoracic glands secrete moulting hormone (MH), called Ecdysone under the
influence of brain hormone.
 Moulting hormone helps in insects in the initiation and process of moulting.
5. Weismann’s Ring:
 It is found in housefly, flesh fly and blow fly.
 A Small ring like structure present behind the brain and around the aorta, supported
by tracheae.
 It contains three types of glandular cells homologous with other endocrine glands.
CLASSIFICATION OF INSECT
 Insects are invertebrates grouped in the phylum Arthropoda (Arthro-joint, poda-foot)
and subphylum Uniramia.
Characters of the Phylum Arthropoda are
1. Segmented body
2. Segments grouped into 2 or 3 regions (tagma) known as Tagmosis.
3. Renewable chitinous exoskeleton
4. Grow by molting.
5. Bilateral symmetry ofbody.
6. Body cavity filled with blood and called as haemocoel.
7. Tubular alimentary canal with mouth and anus at anterior and posterior ends.
8. Dorsal heart with valve like ostia.
9. Dorsal brain with ventral nerve cord.
10. Striated muscles (with dark and light bands).
11. No cilia (hair like vibratile structure on the surface of the cell).
12. Paired, segmented appendages
Phylum Arthropoda is classified in to 7 classes
1. Onychophora (claw bearing) e.g. Peripatus
2. Crustacea (Crusta - shell) e.g. Prawn, crab, wood louse

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3. Arachnida (Arachne - spider) e.g. Scorpion, spider, tick, mite
4. Chilopoda (Chilo - lip; poda - appendage) e.g. Centipedes
5. Diplopoda (Diplo - two; poda- appendage) e.g. Millipede
6. Trilobita (an extinct group) e.g. Trilobite
7. Hexapoda (Hexa- six; poda-legs) or Insecta (In- internal; sect – cut) e.g. Insects.
1. Class : Onychophora
♠ Animals forms the connecting link between the phylum Annelida & Arthropoda
♠ Animals are terrestrial and worm like
♠ Body is unsegmented, externally with numerous pairs of unjointed legs
2. Class : Trilobita
♠ Animals are marine forms with 3 lobed molded body, Unsegmented head (Cephalon),
flexible trunk (Thorax) and (Pygidium) unsegmented tail
♠ Head possesses single pair of antennae
♠ Body is unsegmented, externally with numerous pairs of unjointed limbs
3. Class: Crustacea
♠ Animals are predominantly marine
♠ Body is divided in to Cephalothorax & Abdomen
♠ Animals possess five pairs of legs and two pairs of antennae
♠ Respiration by means of gills
4. Class : Arachnida
♠ The body is divided into cephalothorax and abdomen.
♠ Bears four pair of legs
♠ Instead antennae Chelicerae & Pedipalpi present
♠ Respiration by lung books and tracheae
5. Class : Myriapoda
♠ The body is divided into head and trunk
♠ Bears single pair of antennae
♠ Each body segment bears appendages
♠ Respiration by lung books and tracheae
Sub Class: Diplopoda
♠ Animals with two pair of legs to each segment
Sub Class: Chilopoda
6. Class : Insecta
♠ The body is divided into distinct regions, i.e. Head, Thorax and Abdomen.
♠ Single pair of antennae on head.
♠ Three pairs of legs on thorax.
♠ Two pairs of wingson thorax.

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♠ The genital opening are situated on 8th
and 9th
abdominal segments
♠ Respiration by means of tracheae
♠ Undergo Metamorphosis
♠ Possess exoskeleton made up of hard cuticle which plays important role for survival
♠ Excretion is mainly by malpighian tubules which help in maintaining ionicbalance.
Scientific Nomenclature: -
Caroles Linnaeus (1707 – 1778) in his tenth edition of ‘systema naturae’published
in 1758 used the binomial system of nomenclature for the first time for both plants and
animals. This double naming in Latin one for the genus and thesecond for the species has
been universally accepted.
Taxonomy – (Taxis = arrangement & Nomus = laws)Taxonomy is the science of
classification. It can be defined as placing biological organisms or forms in order. Simpson
(1961) has defined taxonomy as the theoretical study of classification including basis,
principles, procedures and rules. Taxonomy includes nomenclature and classification.
Systematics - The science of study of kind and diversity of organisms and any or all
relations among them. Systematics includes taxonomy and evolution.
Systematic position of insect
Invertebrates
Kingdom: Animalia
Phylum: Arthropoda
Sub-phyllum: Uniramia
Class: Insecta/Hexapoda
Sub class: Pterygota /Apterygota
Order:
Suborder:
Super family:
Family:
Subfamily
Genus:

79
Species
The basic biological unit in the classification is species.
 Species:These are a group of individuals which are similar in their structure,
capable of interbreeding and producing fertile off spring.
 Subspecies:It is an aggregate of phenotypically similar populations of a species
and differing taxonomically from other populations of the species.
 Genus:A group of species having some definite similar characters or relationships is
called a geneus.
 Subfamily:It is a group of allied genera to form a subfamily.
 Family:It is a taxonomic category containing a single genus or a group of genera of
common phylogenetic origin which is separated from related families by a decided
gap. Such families showing similar characters form order.
 The class insecta is divied in to two subclasses Apterygota and Pterygota.
Class – Insecta
Sub class 1. Apterygota
Order 1: Thysanura (Bristle tails, Silverfish, firebrats)(Thysan-fringed, Ura-tail)
Order 2: Diplura (Diplurans)(Di-two; Ura-tail)
Order 3: Protura (Telson tails)(Pro-first, Ura-tail)
Order 4: Collembola (spring tails, snow fleas)(coll-glue; embol-peg)
Sub class 2: Pterygota
Exopterygota (Insects having simple metamorphosis)
Order 5: Ephemeroptera (May flies)
Order 6: Odonata (Dragon flies & damsel flies)
Order 7: Plecoptera (Stone flies)
Order 8: Grylloblattodea (Grylloblattids)
Order 9: Orthoptera (Locusts and grass hoppers)
Order 10: Phasmida (Walking sticks, leaf insects & stick insects)
Order 11: Dermaptera (Ear wigs)
Order 12: Embioptera (Web spinners)
Order 13 Dictyoptera (Cockroaches and mantids)
Order 14: Isoptera (White ants or termites)
Order 15: Zoraptera (Zorapterans)
Order 16: Psocoptera ( Psocids, book lice)
Order 17: Mallophaga (Bird lice)
Order 18: Siphunculata or Anoplura (sucking lice)
Order 19: Hemiptera (Plant bugs)

80
Order 20: Thysanoptera (Thrips)
Endopterygota (Insects having complex metamorphosis)
Order 21: Neuroptera (Ant lions and lace wings)
Order 22: Coleoptera (Beetles, weevils)
Order 23: Strepsiptera (Stylopids)
Order 24: Mecoptera (Scorpion flies)
Order 25: Siphonoptera (Fleas)
Order 26: Diptera (Flies, midges, mosquitoes)
Order 27: Lepidoptera (Moths and butterflies)
Order 28: Trichoptera (Caddis flies)
Order 29: Hymenoptera (Ants, bees, wasps)
 The class Insecta is divided in to 29 orders (4 in Apterygota and 25 in Pterygota).
The class Insecta has two subclasses viz., Apterygota and Pterygota.
Sr.
No.
Apterygota Pterygota
1 Primarily wingless insect Winged or secondarily
wingless insect
2 Metamorphosis is totally absent or slight present. Present
3 Mandibles articulate with head capsule at a single point. double
4 Pleural sulcus in thorax is absent. Present
5 Pregenital abdominal appendages Absent. present
The sub class Pterygota has two divisions viz.,Exopterygotaand Endopterygota
Character Exopterygota Endopterygota
Wing development External Internal
Metamorphosis Incomplete (Hemimetabola) or gradual Complete (Holometabola)
Pupal stage Absent Present
Immature stage Egg, Naiad or Nymph, Adult Egg, Larva, Pupa, Adult
No. of orders 16 09
STUDY OF INSECT ORDERS
1. ORDER: ORTHOPTERA(Orthos - Straight; Ptera-wings)
E.g.Grasshoppers, Locust, Katydids, Mole cricket, house and field cricket.
 Economic Importance: Majority of insects are phytophagous like grasshopper,
locust some create noisy loud sound.
Characters:
 Antenna is filiform.

81
 Mouthparts are mandibulate.
 Head position is hypognathous.
 Prothorax is large and distinct.
 Legs are saltatorial type.
 Legs normally developed, or forelegs modified for digging (fossorial) as in
mole crickets or hind legs modified for jumping (saltatorial) as in grasshopper.
 Forewings are leathery, thickened and known as Tegmina and Hind wings are
membranous.
 Specialized stridulatory (sound-producing) organs are present. Usually males
alone can produce sound.
 Auditory or tympanal (hearing) organs are also well developed and are located
on either side of the first abdominal segment or at the base of fore tibia.
 Cerci are short and unsegmented.
 Metamorphosis is gradual. (simple or incomplete)(Egg – Nymph - Adult)
 Ovipositor is well developed in female on 7 & 8th
abdominal sternum.
 Male genitalia on 9th
abdominal sternum.
This order is sub divided into two suborders, viz., Caelifera and Ensifera.
Sr.
No.
Caelifera Ensifera
1 Antennae are shorter than bodyless than 30
segments
Antennae are longer than body more
than 30 segments
2 Tympanum is found on the lateral side of the
first abdominal segment.
Tympanum is found on the fore tibia.
3 Diurnal(Active at day) Nocturnal(Active at night)
4 Feed on monocot plants Feed on dicot plants
5 Eggs laid in soil. Eggs laid in plant tissue
6 Ovipositor is short Ovipositor is more or less elongate.
7 Stridulatory organ (Femoro-alary type) Stridulatory organ (Tegminal)
8 Family: Acrididae: Short horned
grasshoppers, Surface grasshoppersand
locusts.
Families:
1. Tettigonidae:Long horned
grasshoppers, Katydids and bush
crickets.
2. Gryllidae: House and fieldCrickets.
3. Gryllotalpidae: Mole crickets.
2. ORDER: DICTYOPTERA(Dictyon - Network; Ptera – wings)
♣ E.g. Cockroaches and Preying Mantid
 Economic Importance : Cockroaches are household pests and Mantid predatory in
habit
Characters:
 Head is usually hypognathous.

82
 Antenna is filiform/ cetaceous.
 Mouthparts are mandibulate type.
 Forewings are tegmina and Hind wings are large membranous.
 Prothorax with pronotum covering
 Cerci are short and many segmented.
 Fore legs is walking/raptorial type.
 Eggs are contained in an ootheca.
 Metamorphosis is gradual. (simple or incomplete)
 Female with reduce ovipositor on 7th
abdominal sternum.
 Male genitalia on 9th
abdominal sternum.
 Dictyoptera is divided into two suborders viz., Blattaria (cock-roaches) and
Mantodea (preying mantids). The important families are Blattidae and
Mantidae.
Differences between Blattaria and Mantodea
Sr.
No.
Blattaria Mantodea
1 Head is completely covered with
pronotum.
Head is not covered with pronotum.
2 Two ocelli are present. Three ocelli are present.
3 Legs cursorial (All pairs) Fore legs is raptorial type.
4 Proventriculus with powerful teeth. Proventriculus not powerful teeth.
5 Eggs laid in ootheca Eggs laid in spaumaline
6 Omnivorous Carnivorous
7 No mimicry found Mimicry found
8 Nymph not cannibalistic Nymph cannibalistic
Family: Blattidae- e.g. Cockroaches Family: Mantidae- e. g. preying mantids
3. ORDER: ODONATA (Odous - Tooth; anus – having), E.g. Dragonflies and
damselflies.
 Economic Importance: Adults are aerial predators. They are able to catch, hold and
devour the prey in flight. Naiads are aquatic predators. Adult predacious on
mosquitoes, Houseflies etc. and nymph feed on mosquito larvae.
Characters:
 Medium to large sized insects. They are attractively coloured.
 Head is Mobile and attached to slender neck
 Compound eyes are large. Three ocelli are present.

83
 Antennae is filiform
 Chewing and biting type of mouth parts
 Wings are membranous. Wings have a dark pterostigma towards the costal
apex.
 Prothorax is reduced; meso and meta thorax is fused.
 Basket like legs present to catch prey in flight
 Abdomen is long and slender.
 Metamorphosis is incomplete with three life stages. The naiad is aquatic.
 Labium is greatly elongated, jointed and bears two hooks at apex. It is called
mask. It is useful to capture the prey.
 Respiration by means of rectal or caudal gills.
 Immature stage of Odonata is called “Naiads”
 There are three sub-orders. Anisoptera, Zygoptera and Anisozygoptera.
Differences between Anisoptera and Zygoptera
ANISOPTERA
(Anisos = Unequal & Ptera = Wing)
ZYGOPTERA
(Zygon = Equal & Ptera = Wing)
Adult Characters
1. Strong fliers 1. Weak fliers
2. Compound eyes large meet each other
(Holoptic)
2. Compound eyes button like, wide apart
(Dichoptic)
3. Hind wings basally broader than
forewings
3. Both Pair equal with identical venation
4. Wings spread laterally at rest 4. Wings held at an angle above abdomen
NYMPH (Naid) CHARACTERS
1. Stout and robust 1. Weak and fragile
2. Rectal gills present 2. Caudal gills present
3. Jet propulsion Mechanism present 3. Absent
E. g. Dragonfly E. g. Damselfly
4. ORDERS: ISOPTERA(Iso - Equal; Ptera - wing)E. g. Termites (White ants)
 Economic Importance: Termites are nature's scavengers. They convert logs, stumps,
branches etc, to humus. Many are injurious to crops, furniture and wood works of
buildings
Characters:
 They are ancient polymorphic, social insects living in colonies
 White, soft bodied insects.
 Antennae are short and moniliform.

84
 Compound eyes present in winged forms.
 Mouthparts are adapted for biting and chewing.
 Wings are membranous. Wings are present only in sexually mature forms
during swarming season.(Deciduous type)
 Tarsi are always 4 segmented
 Circi are short
 External genital organs are lacking in both the sexes.
 Metamorphosis simple or incomplete.
 Caste system: Following are the difference castes that are usually seen in
atermite colony.
 Workers is the damaging caste
A) Reproductives Cast;-
a) Primaryreproductive (King& Queen)
b) Supplementary reproductive
B) Sterile Cast;-
a) Workers
b) Soldiers
 Important families:-
1. Termitidae- e.g. Termes spp, Odontotermes spp.
2. Kalotermitidae- e.g. Dry wood termites.
5. ORDER: THYSANOPTERA (Thysano: Fringed and Pteron: wing), E.g. Thrips
 Economic Importance: Most of the thrips species belong to the family Thripidae and
are phytophagous. They suck the plant sap. Some are vectors of plant diseases. Few
are predators.
Characters:
 They are minute, slender, soft bodied insects.
 Mouthparts are rasping and sucking.

85
 Right mandible is absent Hence mouthparts are asymmetrical.
 Antennae short moniliform
 Fringed wings are present
 Prothorax is free and well develops.
 Abdomen is elongate with 10-11 segments, usually tapering posteriorly
 Cerci absent
 Metamorphosis is incomplete with inactive pupa like instars (Aberrant
hemimetabola)
 Parthenogenetic type of reproduction is very common and in many species
males are rarely seen.
 This order is subdivided into two suborders.
 1. Terebrantia: Important family is Thripidae, e.g Onion Thrips
 2. Tubulifera: Important family is Phaleothripidae e.g Olive Thrips
6. ORDER: HEMIPTERA (Hemi - half; Ptera – wing)
E.g. Bugs, Aphids, Whiteflies, Mealy bugs, Scales etc
Characters:
 Head is opisthognathous.
 Mouthparts are piercing and sucking type.
 Forewings (Hemielytra) are either uniformly thickened throughout distally
membranous.
 Cerci are always absent.
 Metamorphosis usually incomplete.
 Alimentary canal is suitably modified (filter chamber) to handle liquid food.
 There are two suboders viz., Heteroptera and Homoptera
Differences between Heteroptera and Homoptera
Sr.
No.
Heteroptera
(Hetero-different; Ptera-wing)
Homoptera
(Homo-uniform; Ptera-wing)
1 Head is porrect or horizontal Head is deflexed
2 Pronotum usually large Pronotum small and collar like
3 Forewings hemelytra Forewings uniform in consistency
4 Wings fold flat over the body atrest Wings held roof like over the body
5 Tarsi – 3 segmented antennae 4-5segmented Tarsi 1-3 segmented antenna 3-

86
10segmented
6 odoriferous glands arepresent wax glands are present
7 Herbivorous, predaceous orblood sucking. Herbivorous
8 Both terrestrial and aquatic Terrestrial
9 Honey dew secretion uncommon Honey dew secretion common
10 Important families of heteroptera
1. Cimicidae: (Bed bugs)
2. Tingidae: (Lacewing bugs or Tingid bug)
3. Miridae: (Plant bugs or Leaf bugs)
4. Lygaeidae: Dusky cotton bug
5. Pyrrhocoridae: Red cotton bug
6. Coreidae: Rice earhead bug,Tur pod bug,
7. Pentatomidae: (Stink bugs, Painted bug)
8. Belostomatidae: (electric light bugs)
Important families of homoptera
1.Cicadellidae: (Leaf hoppers or
Jassids)
2. Delphacidae : (Delphacids)
3. Aleyrodidae: (Whiteflies)
4. Aphididae: (Aphids)
5. Coccidae: (Scale insects)
6. Kerridae: (Lac insect)
7. Pseudococcidae: (Mealy bugs)
7. ORDER: NEUROPTERA(Neuron-nerve; Ptera - wings), E. g. Green lace wings,
Ant lions, Alder fly, Snake fly
 Economic Importance: Insects are predacious (on aphids, White flies, thrips) –
beneficial, Dobson flies called hellgrammites use for fish baiting.
Characters:
 They are soft bodied insects
 Antenna is filiform
 Mouthparts are chewing type in adults.
 Two pairs of similar membranous wings in rest form roof on abdomen
 Circi absent
 Larva is carnivorous, campodeiform
 Pupa is Exarate, decticous.
 Pupation takes place in a silken cocoon.
 Malpighian tubules are modified as silk glands.
 Abdomen without cerci.
 Metamorphosis complete type (Egg – Larva – Pupa - Adult)
 Classification: This order is subdivided into two suborders viz., Megaloptera
and Planipennia.
Sub order: Planipennia:
1. Chrysopidae: (Green lacewings, Goldeneyes, Stink flies, Aphid lions)
2. Mantispidae: (Mantispidflies).
3. Myrmeleontidae: (Ant lions)
4. Ascalaphidae: (Owlflies)

87
8. ORDER: LEPIDOPTERA (Lepidos - scales; Ptera – wings)
E. g. Moths, Butterflies, Skippers
Characters:
 Head relatively small free with small neck. Compound eyes are relatively
large; two ocelli present one on each side close to the margins of compound
eyes.
 Mouthparts in adults are of siphoning type. Mandibles are absent.
 Antennae are clubbed in buterflies and filamentous in moths
 Wings are membranous and scaly.
 Wings are coupled by either frenate or amplexiform type of wing coupling.
 Larvae are called caterpillars usually polypod-eruciform type.
 Two to five pairs of fleshy unsegmented prolegs are found in the abdomen. At
the bottom of the proleg, crochets are present.
 Pupa is generally adecticous and obtect
 Adults are harmless except fruit sucking moths.
 Undergo complete metamorphosis.
There are three sub-orders. Zeugloptera, Ditrysia, Monotrysia.
Sr.
No.
Zeugloptera Monotrysia Ditrysia
1 Adults with functional
mandibles
Adults without functional
sometimes with vestigial
mandibles
Adults without functional
mandibles
2 Female bursa copulatrix
opening into common
oviduct
Female with 1 or 2 genital
opening behind sternite
Female with opening bursa
copulatrix on sternite
3 Female insects have one
pore.
Female insects have two
pores.
Important familyof suborder Ditrysia:-
Family: Noctuidae - This is the largest family in this order. E. g. Army worms, cutworms,
Spodoptera, Helicoverpa, Fruit sucking moth, Castor semilooper.
Family: Gelechidae– E. g. Potato tuber moth, Pink bollworm, Groundnut leaf miner,
Angoumois grain moth.
Family: Pyralidae–E. g. Cotton leaf roller, Jowar stem borer, Wax moth
Family: Pterophoridae–E. g. Tur plume moth
Family: Arctiidae–E. g. Hairy caterpillar

88
Family: Hesperiidae–E. g.Rice skipper
Family: Shingidae–E. g. Sesamum and Sweet potato leaf eating caterpillar
Family: Papilionidae–E. g. Lemon butterfly
Family: Lycanidae–E. g. Anar caterpillar
Family: Pieridae–E. g. Cabbage butterfly
Family: Bombycidae–E. g. Mulberry silk worm
Family: Saturnidae–E. g. Tasar and Erri silk worm
Differences between moths and butterflies
Sr.
No.
Moths Butterflies
1 Nocturnal in habit Diurnal in habit
2 Antennae either Pectinate or bi Pectinate
plumose type
Antennae Clavate type
3 Ocelli Present Ocelli Absent
4 Mandibles Present Mandibles Absent
5 Wing coupling Frenate type Wing coupling amplexiform type
6 Abdomen Large and stout Abdomen Comparatively small and slender
7 Obtect pupa within a cocoon Obtect pupa without cocoon.
8 At rest, wings held roof like on body At rest, wings held erect straight upward.
9. ORDER: HYMENOPTERA (Hymen - membrane; Ptera - wings.)
E. g. Wasps, bees, ants, sawflies, Parasitoids etc
 Economic Importance: Red ant, mustard saw fly are crop pest. Many insects are
beneficial parasitoids or pollinators
Characters:
 This is the most beneficial order in the class insecta comprising of parasites, predators
and bees involved in poliination and honey production. Most of them are social
living
 Mouth parts are biting type modified for lapping or sucking
 Wings are membranous
 Wing venation ishamuli type.
 Abdomen is basally constricted. The first abdominal segment is called propodeum. It
is fused with metathorax.The second segment is known as pedicel which connects the
thorax and abdomen. Abdomen beyond the pedicel is called gaster or metasoma
 Larvae are known as grubs with well developed head and usually apodous and
eucephalous
 Pupa exarate and a cocoon is generally present
 Metamorphosis complete and complex also.
 Fertilized eggs develop into females and males are produced from unfertilized eggs.
Males are haploid and females diploid.

89
 This order is subdivided into two suborders; Symphyta andApocrita
Differences between Symphyta and Apocrita
Sr.
No.
Symphyta Apocrita
1 Abdomen is broadly joined to the thorax Abdomen is petiolated
2 Larva is a caterpillar and it belongs
eruciform type
Larva is a grub and it belongs apodous
eucephalous type
3 Stemmata are present Stemmata are absent.
4 Both thoracic and abdominal legs are
present
Legs are absent
5 Ovipositor is saw like andsuited for
piercing the plant tissues
Ovipositor is not saw like and is suited for
piercing in parasitic groups or for
stingingin other groups.
6 Behavioural sophistication is less. Behavioural sophistication is more
7 They are phytophagous They are generallyparasitic
8 Important families:
Tenthredinidae : (Sawflies)
Important families:
Apidae : (Honey bees)
Vespidae: Wasps
Megachilidae: (Leaf cutter bees)
Formicidae: (Ants)
Braconidae : (Braconid wasps)
Trichogrammatidae: (Egg parasitoids)
10. ORDER: COLEOPTERA (Coleos - Sheath ; Ptera-wing), E. g. Beetles, Weevils
 Economic Importance: It is the largest order. It includes predators, scavengers and
many crop pests. They also damage stored products.
Characters:
 They are minute to large sized insects.
 This is the largest order in class insecta comprising about 1/3rd or 40% of the
known insect species.
 Mouthparts are chewing & biting type.
 Head position is prognathous type
 Antenna is usualy 11 segmented.
 Prothorax is large, distinct and mobile. Mesothorax and metathorax are fused
with the first abdominal segment.
 Forewings are horny or leathery known as elytrait is not used for flight. Hind
wings are membranous with few veins and are useful in flight.
 Legs well developed for walking, running.
 Cerci and a distinct ovipositor are absent.
 Metamorphosis is complete.
 Larvae are often called grubsit is campodeiform or eruciform.
 Pupae adecticous and Exarate.

90
 This order is divided into four suborders, viz., Adephaga (devourers) and
Polyphaga (eaters of many things), Archostemata (wood feeders) and
Myxophaga (Found in wet places
Difference between Adephaga and Polyphaga
Sr.
No.
Adephaga Polyphaga
1 Cicindelidae: (Tiger beetles) Meloidae: (Blister beetles, Oil beetles)
2 Dytiscidae: (True water beetles) Coccinellidae: (Lady bird beetles, Epilachna
beetle)
3 Carabidae: (Ground beetles) Scarabaeidae: (white grub, Dung beetles)
4 Cerambycidae: (Mango stem borer, Grape stem
girdler)
5 Bruchidae: (Pulse beetles, Seed beetles)
6 Tenebrionidae: (Rust red flour beetle)
7 Bostrychidae: (Lesser Grain borers)
8 Melolonthidae: (Chafer beetles, June beetles)
9 Dynastidae: (Rhinoceros beetles)
10 Curculionidae: (Weevils, snout beetles)
11 Chrysomelidae : eg. Red pumpkin beetle
Differences between Beetle and Weevil
Sr.
No.
Beetle Weevil
1 Mouthparts typically chewing type Mouthparts chewing type but modified into
snout like structure.
2 Both pairs of wings present. Hind wing absent.
3 Antennae capitates/ serrate/ Lamellate Antennae clavate
4 Tarsi 3 to 5 segmented Tarsi 4 segmented
5 Larvae oligopod Larvae apodous
11. ORDER: DIPTERA(Di-two; Ptera-wing)
E. g. Housefly, Fruit fly, Horse fly, Pod fly, Stem fly, Mosquito, Midges.Midge fly,
shoot fly, gall fly
 Economic Importance: Considerable number of flies is predacious. some are act as a
vectors for transmission of disease, fruit flies, leaf miners, stem fly and root maggots
are crop pest
Characters:
 They are small to medium sized, soft bodied insects.

91
 Mouth parts sucking type usually forming a proboscis. In many they are
piercing and sucking and in others they are sponging type
 Antennae mostly 3 segmented and Aristate type
 Forewings are larger, membranous and used for flight. Hind wings are highly
reduced, knobbed at the end and are called halters.
 Prothorax and metathorax are small and fused with large mesothorax
 Metamorphosis is complete
 Larvae of more common forms are known as maggots. They are apodous and
acephalous (eruciform). Maggots mostly amphipneustic
 Pupa is generally with free appendages, often enclosed in the hardened last
larval skin called puparium. Pupa belongs to the coarctate type.
 Legs well developed, tarsus usually 5 segmented pulvilli and an empodium
usuallypresent
 This order is sub divided in to three suborders; Nematocera (Thread-horn),
Brachycera (Short-horn ), Cyclorrhapha (Circular-crack
Comparative characters of these sub-orders
Sr.
No.
Nematocera Brachycera Cyclorrhapha
1 Antenna is long and many
segmented in adult.
Antenna is short and
few segmented in adult.
Antenna is aristate in adult
2 Larval head is well
developed.
Larval head is retractile
into the thorax.
Larval head is vestigial with
mouth hooks.
3 Larval mandibles act
horizontally.
Larval mandibles act
vertically
Larval mouth hooks act
vertically.
4 Pupa is weakly obtect. Pupa is exarate. Pupa is coarctate.
5 Adult emergence is through a
straight split in the thoracic
region
Adult emergence is
through a straight split
in the thoracic region.
The split results due to the
pressure applied by an
eversible bladder ptilinum in
the head.
6 Pseudotrachae absent Pseudotrachae present Pseudotrachae present
7 Important families:
Culicidae: Mosquitoes
Cecidomyiidae :Pady gall
fly
Important families:
Asilidae: Robber flies
Tabanidae: Horse flies
Trypetidae: Fruit flies
Agromyzidae: Tur pod
fly, Leaf miner
Important families:
Syrphidae; Syrphid fly
Tachinidae: Tachinid flies
Muscidae: House fly

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