fundamental of entomology all in one topics of entomology

the documents prepared to compiled all the topics of basic entomology

1. Course No. – ENTO-121 TITLE-FUNDAMENTALS OF ENTOMOLOGY Dr. Anita Sharma Asstt . Professor (Entomology)

2. Entomology- Greek word ( Entomon = Insect; Logos = Study) It is the branch of zoology or biological science that deals with the study of insects . INTRODUCTION Insect : - The insects are the tracheate arthropods in which the body is divided in to head, thorax and abdomen possessing 2 pairs of wings. 3 pairs of working legs. 1 pair of antennae. Segmented body. Having complete and incomplete metamorphosis.

3. Insect is Greek word = Cut in pieces or segmented. Insects belong to the Phylum Arthropod a ( Artho = jointed, Poda = Legs) which is the biggest phylum of kingdom Animalia . More than three quarters of the animals on earth are arthropods, and most of these are insects. Kingdom Animalia is classified into twelve phyla. INTRODUCTION

4. Study and use of insects in crime investigations is known as Forensic Entomology . Study of insects related to live stock and veterinary animals is known as Veterinary Entomology . Study of insects in relation to Human beings is known as Medical Entomology . Study of insects in relation to Agriculture is known as Agriculture Entomology Branches of Entomology

5. Topic -1, HISTORY OF ENTOMOLOGY IN INDIA Aristotle (384-322 B.C.)– Father of biological classification . First person grouped insects in winged and wing less groups. He gave the terms like Coleoptera and Diptera . Carolus Linnaeus (1758)– Father of Taxonomy . William Kirby considered as “Founder of Entomology ” because of his significant role in Entomology in the world. He published a book “ An Introduction to Entomology” (1815-1826). Snodgrass R. E. (1875)– referred as a Father of Insect Morphology . He wrote book - Principles of Insect Morphology. Mithan Lal Runwal (1908)– Outstanding work on termites/ white ants. Contributions to ecology, embryology and locust. 1940 - Dr. T.V. Ramakrishna Ayyar published the book " Handbook of Economic Entomology " which met the long felt need of the students of Agriculture and agricultural scientists as well and also known as “Father of Indian Entomology”. Dr.S.Pradhan (1969) - Wrote a "Insect Pests of Crops" and Father of Modern Applied Entomology in India.

6. History of Entomology in India 1758 - 10th edition of Systema Naturae by Linnaeus with only 12 Indian insects which was the earliest record. 1779 - Dr. J.G. Koenig - Medical Officer initiated the work on Indian insects on scientific lines. He also published a special account of the termites of Thanjavu r District. 1782 - Dr. Kerr Published on account of lac insect. 1785 - Asiatic Society of Bengal started in Calcutta and many papers were published in the Societys publications. 1790 - Roxburgh (Botanist) published a detailed account of lac insect. 1791 - Dr. J. Anderson issued a monograph on Cochineal scale insects 1800 - Buchanan ( Traveller ) wrote on the cultivation of lac in India and on sericulture in some parts of South India. Denovan published Natural History of Insects which was the first contribution on the insects of Asia and was revised in 1842 by West Wood. 1875 - Foundation of the Indian Museum at Calcutta

7. 1883 - Bombay Natural History Society was started. After the foundation of these two organisations scientific studies received greater attention in India. Numerous contributions of Indian insects were published in the Journal of the Bombay Natural History. 1893 - Rothney published on Indian Ants (earliest record of biological pest control in India) i.e. White ants attach on stationary items was kept free by red ants. 1897 - Bingham's issued volumes on "Hymenoptera ' (Ants, bees and wasps). Since than volumes on other groups of insects like Coleoptera (beetles), Hemiptera (bugs), Odonata ( dragenfly and damselfly), etc., were published. 1889 - Indian Museum, Calcutta published the Indian Museum Notes in five volumes. 1901 - (Lionel de Nicevelle ) posting of the first entomologist to the Government of India. 1905 - Establishment of Imperial Agricultural Research Institute at Pusa (Bihar). Maxwell Lefroy became first Imperial Entomologist of Govt. of India. 1906 - “Indian Insect Pests” & “Indian Insect Life” Books by Professor Maxwell . Subsequently State Governments also took up entomological work. 1914 - T.B. Fletcher, the first Government Entomologist of Madras State , published his book "Some South Indian Insects".

8. 1916 –”Indian Forest of Economic Importance: Coleoptera ; was published by the first Imperial Forest Entomologist E.P. Stebbing ”. 1921 - Indian Central Cotton Committee to investigate on pests of cotton. 1925 - Indian Lac Research Institute. 1934- Hem Singh Pruthi as Imperial Entomologist, start ‘Entomological Society of India ’ in 1938. Afzal Hussain was the first president of the society and VC were HS Pruthi and Ayyar . 1940 - Dr. T.V. Ramakrishna Ayyar published the book " Handbook of Economic Entomology " which met the long felt need of the students of Agriculture and agricultural scientists as well and also known as “Father of Indian Entomology”. 1968 - Dr. M.S. Mani's "General Entomology" 1969 - Dr. H.s. Pruthi's "Textbook of Agricultural Entomology". Dr. Pradhan's "Insect Pests of Crops“ 1946 - Government of India started the "Directorate of plant protection, quarentine and storage.". 1960 - "The Desert Locust in India" monograph by Y.R. Rao . 1969 - "The monograph on Indian Thysanoptera " by Dr. T.N. Ananthakrishnan

9. 1912– Plant Quarantine Act. 1914– Destructive Insects and Pests Act ( DIPA ). 1916– Imperial Forest Research Institute at Dehradun . 1925– Indian Lac Research Institute started at Ranchi. 1937– A laboratory for storage pests was started at Hapur , U.P. 1937- Establishment of Entomology division at IARI New Delhi. 1939– Locust Warning Organization established at Jodhpur. 1946– ‘Directorate of Plant Protection, Quarantine & Storage at Faridabaad . 1968– ‘Central Insecticide Act’. Institutes/Organizations

10. NCIPM , New Delhi- (National Centre for Integrated Pest Management - 1988). PDBC , Bangalore- (Project Directorate of Biological Control -1993). NBAIR -National Bureau of Agricultural Insect Resources and formerly it is a NBAII, Bengalore in 1957. CIB , Faridabad – Central Insecticide Board. NPPTI , Hyderabad– National Plant Protection Training Institute. Entomological Institutes

11. FACTORS FOR INSECTS ABUNDANCE Measures of dominance 1. More number of species : In the animal kingdom more than 85 per cent of the species belongs to insect group. Total number of insects described so far is more than 9 lakhs . 2. Large number of individuals in a single species: e.g., Locust swarm comprising of 10 9 number of individuals, occupying large area. 3. Great variety of habitats: Insects thrive well under varied conditions. 4. Long geological history : Insects were known to occupy this earth for more than 350 million years, which is a good track record. This has given the insects great variety of adoptions under different conditions.

12. Reasons for dominance Capacity for flight: Insects posess wings, which is the lateral extension of exoskeleton. Insects are the earliest animals and the only flying invertebrates. Flight is used for the following purpose- To seek food, mate, shelter and oviposition sites To colonize in a new habitat and also to exchange habitat. To escape from enemies and unfavourable conditions. To migrate (i.e. for long distance travel e.g. Locusts) Adaptability or Universality: Insects are the earliest groups to make their life on the earth and to occupy vast habitats of soil and water. i . Found in wide range of climatic conditions, from -50 ñ C to 40 ñ C. ii. Psilopa petroli found in crude petroleum well. iii. Ephydra fly living in great salt lake. iv. Every flowering plant providing food for one or many Phytophagous insects. v. Even the decomposing materials serving as food for many Saprophagous insects. vi. Many Carnivorous insects are parasitic on other animals and insects.

13. 3. Size : Majority of insects are small conferring the following physiological and ecological advantages. i . Less space, food, time and energy requirements for development and sustaining life. ii. Energy Utilization maximum. iii. Less gravitational effect. iv. Muscular action and tracheal respiration more effective. v. Easy escape from enemies. 4. 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. Uses: i.Act as external armour ii.Provides space for muscle attachment iii.Prevents water loss

14. 5. Resistance to desiccation : Insects minimise the water loss from their body surface through the following processes. I. Prevention of water loss: i . Lipids and polyphenols present in the Epicuticle acts as water proofing. ii. Was layer with closely packed wax molecules prevents escape of water. iii. Spiracles are closed to prevent water loss. iv. In the egg stage shell development prevents water loss and desication of inner embryos. II. Conservation of water i . Capable of utilizing metabolic water ii. Rectal resorption of water from faeces . iii. Terrestrial insects use less quantity of water to remove the nitrogenous waste (Uric acid) which is water insoluble. 6. 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.

15. 7. Reproductive potential: Reproductive potential of insect is high due to the following reasons: i Egg laying capacity (fecundity) is high. e.g., Queen termite lays 6000 - 7000 eggs per day for 15 long years. ii. Development period is short. e.g., Corn aphid produces 16 nymphs per female which reaches the adulthood within 16 days. There by one generation is completed within a short period of 16 days, which favours greater genetic changes in the insect population, like quicker development of insecticide resistant strains. iii. Careful selection of egg lying sites and protection of eggs. iv. Exhibits parental care like progressive provisioning (e.g. bees) and mass provisioning (e.g. Wasps) v. Presence of special types of reproduction other than oviparity and viviparity . * Polyembryony : Development of many individuals from a single egg. e.g. parasitic wasps. * Parthenogenesis : Reproduction without male or without fertilization, e.g. aphids * Paedogenesis : Reproduction by immature stages. e.g. certain flies.

16. 8. Complete metamorphosis: More than 82 per cent of insects undergo complete metamorphosis ( Holometabolous insects) with the following four stages. i . Egg: Inactive, inexpensive, inconspicuous and embryo develops inside. ii. Larva: Active, feeds, digests, grows and store food. iii. Pupa: Inactive, internal reorganisation and resist adverse conditions. iv. Adult: Active, reproduce and disperse. As the larval and adult food sources are different, competition for food is less. 9. Defense mechanisms: By using the following defense mechanisms, insects escape from the enemies to increase their survival rate. i . Behavioural : Thanatosis - insects pretends as if dead. e.g. some beetles. ii. Structural e.g. hardened forewings of beetles known as elytra protect the beetles from predation of birds. iii. Colourational : Presence of protective colours . e.g.Stick insects iv. Chemical : Presence of defensive chemicals. e.g. Bees producing venom 10. Hexapod locomotion: Insects uses 3 legs at a time during locomotion, while the remaining 3 legs are static, which gives greater stability.

17. POSITION OF INSECTS IN ANIMAL KINGDOM

18. POSITION OF INSECTS IN ANIMAL KINGDOM AND ITS RELATIONSHIP WITH OTHER ARTHROPODA Classification: 7 classes. Phylum : Arthropoda Classes : 1. Onychophora (claw bearing)e.g. Peripatus , has similarities with arthropoda like antenae , open circulatory system, walking legs with claw and tracheal system. 2. Crustacea ( Crusta - shell)e.g. Prawn, crab, wood louse 3. Arachnida ( Arachne - spider)e.g. Scorpion, spider, tick, mite 4. Chilopoda ( Chilo - lip; poda - appendage)e.g. Centipedes (carnivorous) 5. Diplopoda ( Diplo - two; poda - - appendage)e.g. Millipede ( scavengers) 6. Trilobita (an extinct group)- The dominant arthropodes in the early Paleozoic seas (many million ago) 7. Hexapoda or Insectae.g . Insects.

19. Characters of the Phylum Arthropoda : ( Arthro -joint, poda -foot) i . Segmented body ii. Segments grouped into 2 or 3 regions known as Tagmosis iii. Renewable chitinous exoskeleton iv. Grow by moulting v. Bilateral symmetry vi. Body cavity filled with blood- Haemocoel vii. Tubular alimentary canal with mouth and anus viii. Dorsal heart with ostia ix. Dorsal brain with ventral nerve cord x. Striated muscles xi. No cilia xii. Paired segmented appendages

20. Insect body wall – Integument/Exoskeleton External covering – ectodermal in origin Rigid, flexible, lighter, stronger and variously modified Insect Integument: Structure and Function

21. Consists of 3 layers : Structure Integument Cuticle Epidermis Basement membrane

22. Outer non-cellular layer – has 2 sub-layers Epicuticle : outer most layer – very thin – devoid of chitin Differentiated into 5 layers: Cement layer – outer most layer – made of lipid and tanned protein – protects wax layer. Wax layer – contains closely packed wax molecules – prevents desiccation Cuticulin – Non-chitinous polymerised lipoprotein layer – barrier to ions Outer Epicuticle Inner Epicuticle (It contain wax filaments) Cuticle. ...

23. Procuticle – divided into 2 – Outer exocuticle & Inner Endocuticle . Exocuticle : Outer layer – much thicker – composed of Chitin & Sclerotin – Dark and rigid Endocuticle – Inner layer – thickest layer – made of chitin & Arthropodin – Colourless, soft and flexible. Epidermis: Inner unicellular layer resting on basement membrane – Functions: Cuticle secretion Digestion and absorption of old cuticle Wound repairing Gives surface look

24. Composition .... Chitin: Main constituent of cuticle Nitrogenous polysaccharide and polymer of N- acetylglucosamine . (water insoluble and soluble in acids, alkalies and organic solvents) Arthropodin : Untanned cuticular protein (water soluble). Sclerotin : Tanned cuticular protein (water insoluble). Resilin : Elastic cuticular protein – for flexibility of sclerites .

25. Cuticular in growth of body wall – provide space for muscle attachment. 2 types: Apodeme – hollow invagination of body wall (ridge like) Apophysis – Solid invagination of body wall (spine or fingure like) Endoskeleton. ..

26. 31

27. Clothing hairs, plumose hairs. e.g. Honey bee. Bristles. e.g. flies 32

28. Scales - flattened out growth of body wall e.g. Moths and butterflies 33

29. Glandular seta. et. caterpillar 34

30. Sensory setae - associated with sensory neuron or neurons 35

31. Seta - hair like out growth (Epidermal cell generating seta is known as Trichogen , while 36

32. 37 Multicellular e.g. Spur - movable structure Spine - Immovable structure

33. GLANDS Cuticular glands are either unicellular or multicellular. Following are some of the examples . i . Wax gland - e.g. Honey bee and mealy bug ii. Lac gland - e.g. Lac insects iii . Moulting gland secreting moulting fluid. iv . Androconia or scent scale - e.g.moth v . Poison gland - e.g. slug caterpillar 38

34. Wax gland - e.g. Honey bee and mealy bug 39

35. . Lac gland - e.g. Lac insects 40

36. Moulting gland secreting moulting fluid 41

37. Poison gland - e.g. slug caterpillar 42

38. Functions of Body wall i . Acts as external armour and strengthen external organs like jaws and ovipositor ii . Protects the organs against physical aberation , injurious chemicals, parasites, predators and pathogen. iii . Internally protects the vital organs, foregut, hindgut and trachea. iv . Provides space for muscle attachment and gives shape to the body. v . Prevents water loss from the body. vi . Cuticular sensory organs helps in sensing the environment. vii . Cuticular pigments give colour. 43

39. MOULTING ( Ecdysis ) Ecdysis Periodical process of shedding the old cuticle accompanied by the formation of new cuticle is known as moulting or ecdysis . The cuticular parts discarded during moulting is known as Exuvia . Moulting occurs many times in an insect during the immatured stages before attaining the adult-hood. The time interval between the two subsequent moulting is called as Stadium and the form assumed by the insect in any stadium is called as Instar . 44

40. Steps in moulting 1. Behaviroual changes: Larva stops feeding and become inactive . 2. Changes in epidermis: In the epidermis cell size, its activity, protein content and enzyme level increases. Cells divide miotically and increases the tension, which results in loosening of cells of cuticle . 45

41. 3. Apolysis : Detachment of cuticle from epidermis 4. Formation of Sub cuticular space 5. Secretion of moulting gel in the sub cuticular space which is rich with chitinase and protease. 6. New epicuticle formation: Lipoprotein layer ( cuticulin ) is laid over the epidermis. 46

42. 7. Procuticle formation: Procuticle is formed below the epicuticle. 8. Activation of moulting gel: Moulting gel is converted into moulting fluid rich in enzymes. This activates endocuticle digestion and absorption. 9. Wax layer formation: Wax threads of pore canals secrete wax layer. 10. Cement layer formation : Dermal glands secretes cement layer ( Tectocuticle ). 47

43. 11. Moulting : This involves two steps   i . Rupturing of old cuticle: Insect increases its body volume through intake of air or water which enhances the blood flow to head and thorax. There by the old cuticle ruptures along predetermined line of weakness known as ecdysial line ii. Removal of old cuticle: Peristaltic movement of body and lubricant action of moulting fluid helps in the removal of old cuticle. During each moulting the cuticular coverings discarded are the cuticular of legs, internal linings of foregut and hindgut and trachea . 12.Formation of exocuticle : The upper layer of procuticle develops as exocuticle through addition of protein and tanning by phenolic substance . 13.Formation of endocuticle : The lower layer of procuticle develops as endocuticle through addition of chitin and protein. This layer increases in thickness. 48

44. Control of Moulting: It is controlled by endocrine gland like prothoracic gland which secrete moulting hormone. Endocrine glands are activated by prothoracico -tropic hormones produced by neurosecretory cells of brain. 49

45. Moulting: Shedding of old cuticle accompanied by formation of new cuticle is called Moulting or Ecdysis . Detachment of cuticle from the epidermis is apolysis The time interval between two moults is called a stadium The formation of an insect during a stadium is called an instar The cast off skin by an insect is called as exuviae Chitin which makes up the exo -and endocuticle is a nitrogenous polysaccharide formed from long chains N-acetyl D-glucosamine units ( C 8 H 13 O 5 N) n 50

46. BODY SEGMENTATION OF INSECT & INSECT HEAD

47. Cockroach and Grasshopper 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 ”. 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.

48. 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 segments i.e., mouthparts, 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.

49. Fig. General Organization of Insect Body

50. INSECT HEAD

51. It is the foremost part in insect body consisting of 6 segments that are fused to form a head capsule. Labral , antennary, ocular, mandibular , maxillary and labial segments. 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 tentorium which 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.

52. 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 and 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.

53. ( b) Prognathous : (Pro– infront and 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

54. (c) Opisthognathous : ( Opistho – behind and Gnathous Jaw) It is same as prognathous but mouthparts are directed backward and held in between the fore legs. This is also kwown as Hemipteroid or Opisthorhynchous type. Eg : bugs, Mosquito

55. 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 ).

56. Generally insect possess the following sclerites : Vertex: It is the top portion of epicranium which lies behind the frons or the area between the two compound eyes. 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. Facial area below the vertex and above clypeus 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.

57. 5. Occiput : Cranial area between occipital and post occipital suture . 6. Post occiput : It is the extreme posterior part of the insect head that remains before the neck region. 7. Occular sclerites : These are cuticular ring like structures present around each compound eye. 8. Antennal sclerites : These form the basis for the antennae and present around the scape .

58. Fig. Anterior view or face view

59. The common sutures present in head are: Clypeolabral suture: It is the suture present between clypeus and labrum . 2. Clypeofrontal suture or epistomal suture: The suture present between clypeus and frons . 3. Epicranial suture: It is an inverted ‘Y’ shaped suture distributed above the facial region extending up to the epicranial part of the head. 4. Occipital suture: It is ‘U’ shaped or horseshoe shaped suture between epicranium and occiput .

60. 5. Genal suture: It is the sutures present on the lateral side of the head i.e. gena . 6. 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. 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.

61. Insect Thorax And abdomen

62. Thorax Middle tagma Three segmented - pro, meso and meta Meso and meta thorax with wing are called as Pterothorax Thorax is made of three scleritic plates 1. dorsal body plate - Tergum or Nota 2. ventral body plate ( Sterna ) 3. lateral plate ( Pleura )

63. Thoracic nota 3 segments - pronotum , mesonotum & metanotum respectively Pronotum - undivided & Saddle shaped in grass hopper, Shield like in cockroach Pterothoracic notum - h ave 3 transverse sutures ( Antecostal , Pre scutal and Scuto-scutellar ) & 5 tergites ( Acrotergite , Prescutum , Scutum , Scutellum and Post- scutellum )

64. Thoracic sterna Vental body plate - prosternum , mesosternum and metasternum Made up of a segmental plate called Eusternum and a intersternite called Spinasternum Eusternum - made of three sclerites - presternum , basisternum and sternellum

65. Thoracic pleura Lateral body wall between notum & sternum Selerites of pleuron is called as pleurites fuse to form Pleural plate Pleural plate is divided into anterior episternum and posterior epimeron by Pleural suture Pterothoracic pleuron provides space for articulation of wing and Two pairs of spiracles are also present in the mesopleuron and metapleuron .

66. ABDOMEN Third and posterior tagma This tagma is made up of 9-11 Uromeres (segments) and is highly flexible abdominal segments are interconnected by a membrane called conjunctiva Each abdominal segment is made up of only two sclerite 1. Tergum 2. Sternum

67. ABDOMEN Eight pairs of spiracles in - first eight abdominal segments in addition to a pair of tympanum in the first abdominal segment Eight and ninth segments - female genital structure Ninth segment - male genital structure . Cerci

68. INSECT ANTENNAE: STRUCTURE, FUNCTIONS AND MODIFICATIONS

69. 75 What is Antenna (Plural= Antennae) ? “Antennae are paired , freely mobile , segmented sensory appendages articulated with the head in front of or between the eyes . Antennae are also known as feelers .” These are well developed in adults and poorly developed in immature stages . Antennae are absent in order Protura and Class Arachnida while 2 pairs of antennae present in Class Crustacea .

70. 76 Structure of Antenna “Antennae are multi segmented and may be divided into 3 parts:- Scape :- It is the basal segment of a antenna, by which it is attached with the head . Pedicel :- It is the second segment of antenna which is shorter than scape . This segment having a sensory apparatus named ‘Johnston organ’. Flagellum :- It is the last segment of antenna which consists the remaining divisions of antenna and it greatly varies in its form and structure . It is also known as Clavola .

71. 77 Structure of Antenna

72. 78 Functions of Antennae The main function of antenna is sensory , which is modified according to habit and habitat of insect as given below:- Organs of smell :- Some insects have smell organs on their antennae by which they recognise their food . E.g. Ant, Honey Bee and Jiant moths .

73. 79 Organs of taste :- Some insects have taste hairs on their antennae by which they recognise the taste of their food . E.g. Cockroach .

74. 80 4. Chordotonal Organs :- Hearing organs ( Jhonston’s organ ) found in second segment ( pedicel ) of antenna. e.g. Male mosquito, Green bottle fly and Paper wasp etc. 5. Sexual Dimorphism :- Some insect belonging to the order Diptera and Hemiptera , having different type of Antenna in male and female, which help in sexual dimorphism . e.g. Male and Female Mosquito .

75. 81 Other Functions :- (a). Help the mandibles for holding the prey . (b). Useful for clasping the female during copulation . (c). Butterfly bears some transmitting and receiving organs in their antennae.

76. 82 Modifications of Antennae On the basis of shape and structure, the antennae may be following type:- Setaceous :- These are bristle like antennae, in which segments gradually decrease in size from base to apex and tappering into a point , presenting a whip like structure. e.g. Cockroach and Cricket .

77. 83 2. Filiform (Thread like ):- It is thread like antenna in which segments are uniform in thickness throughout from base to apex and never ends with bristle . e.g. Insect of order Orthroptera , Coleoptera namely Grasshopper and Ground Beetle .

78. 84 3. Moniliform (Like string of beads ):- Such type of antennae have globular or oval shaped segments with uniform thickness from base to apex , by which it looks like string of beads . It have constriction between the joints . e.g. Insect of order Isoptera namely Termite.

79. 85 4. Pectinate (Comb like ):- This is a comb like in structure in which each segment of the antenna possess long projection on one side , giving comb like appearance . e.g. Insect of order Lepidoptera namely Moth of Sugarcane root borer.

80. 86 5. Bipectinate (Double Comb like ):- In this type of antenna, each segment has the long projections on both side , giving double comb like appearance. e.g. Insect of order Lepidoptera namely Silk Moth.

81. 87 6. Serrate (Saw like ):- In this type of antenna, each segment is more or less triangular and projected on one side , which giving teeth of saw like appearance. e.g. Insect of order Coleoptera namely Pulse beetle.

82. 88 7. Flabellate (Feather like ):- In this type of antenna, in which projections of the flagellum become long and form a feather like structure , which is known as flabella . e.g. Insect of order Coleoptera namely Cedar Beetle.

83. 89 8. Plumose ( bursh like with dense hairs ):- In this type of antenna, each segment has the whorls of hairs arise from their joints and look like plumose. e.g. Insect of order Diptera namely Male Mosquito.

84. 90 9. Pilose ( bursh like with sparse hairs ):- In this type of antenna, each segment has the whorls of hairs arise from their joints like plumose but whorl contains less number of hairs . e.g. Insect of order Diptera namely Female Mosquito.

85. 91 10. Whorled :- Basically these are the setaceous , filiform or moniliform type of antennae in which each segment has a whorl of bristle at every joint . e.g. Insect of order Hemiptera namely Male of Mango Mealy Bug.

86. 92 11. Clavate (Clubbed ):- In this type of antenna, segments gradually increase in diameter towards the tip and last segment finally ending into a round core, look like club . e.g. Insect of order Lepidoptera namely Butterfly.

87. 93 12. Capitate (Clubbed with Knob ):- In this type of antenna, segments gradually increase in diameter towards the tip and suddenly last 3-5 segments enlarge to form a knob like structure. e.g. Red Rust Flour Beetle .

88. 94 13. Lamellate (Plate like ):- This is a modification of capitate antennae in which terminal segments extended on the side to form leaf like plate instead of forming the knob . e.g. Rhinoceros Beetle, Dung Rollers etc .

89. 95 14. Geniculate (Elbowed ):- In this type of antenna, the scape is greatly elongated , pedicel is short and flagellum is made up of small segments which make a bent on the scape look like knee . e.g. Ants, Honey Bee etc.

90. 96 15. Aristate (With arista ):- In this type of antenna, scape is smaller and broader , pedicel is longer than scape . The flagellum is longer than both and bears heavy bristle known as arista . e.g. House Fly .

91. 97 16. Stylate (With style ):- In this type of antenna, last segment of flagellum is modified into a long bristle known as style. e.g. Snipe fly, Robber fly.

92. 98 17. Fusiform :- In this type of antenna, scape is smaller and thin , while pedicle is larger and flagellum is modified into a hook like structure. e.g. Sphingid Moth.

93. DIFFERENT TYPES OF MOUTHPARTS Mouthparts very greatly among insects of different orders but there are two main functional groups: 1. Mandibulate Biting and Chewing type 2. Haustellate Chewing and lapping type Rasping and sucking type Piercing and sucking type Sponging type Siphoning type 3.Exceptional Mask type Degenerate type

94. Mandibulate (chewing) mouthparts -are used for biting and grinding solid foods Examples: Dragonflies and damselflies (order Odonata ), termites (order Isoptera ), adult lacewings (order Neuroptera ), beetles (order Coleoptera ), ants (order Hymenoptera), cockroaches (order Blattaria ), grasshoppers, crickets and katydids (order Orthoptera ), caterpillars (order Lepidoptera). Adult Lepidoptera have siphoning mouthparts. Haustellate mouth parts -are primarily used for sucking liquids They possess stylets or not. Stylets are needle-like projections used to penetrate plant and animal tissue. The modified mandibles, maxilla, and hypopharynx form the stylets and the feeding tube. After piercing solid tissue, insects use the modified mouthparts to suck liquids from the host. Some haustellate mouthparts lack stylets . Unable to pierce tissues, these insects must rely on easily accessible food sources such as nectar at the base of a flower. One example of nonstylate mouthparts are the long siphoning proboscis of butterflies and moths (Lepidoptera).

95. BITING AND CHEWING MOUTH PARTS ORDER: Orthoptera , eg : grasshopper Mouth parts are typical mandibulate type useful for biting, chewing and consisting of Labrum (upper lip) Mandibles ( Ist pair of jaws) Maxillae (first maxilla-2nd pair of jaws) Labium (second maxilla or lower lip) Hypopharynx (tongue).

96. Labrum : A simple plate like structure situated below the clypeus on the anterior side of the head and moves up and down. The functions of the labrum are to close the front of the moth cavity, protect the mandibles, pull the food into the mouth.

97. Mandibles: They are the first pair of jaw. Also called true jaw. Paired, un segmented, heavily sclerotized jaws lying immediately below the labrum. Articulate with the head capsule side wise by means of two joints; ginglymus and condyle . Possess two types of inner teeth; incisors (cutting teeth) and molars (grinding teeth). Adopted for cutting and masticating the food material.

98. Maxillae: Paired segmented structures lying below the mandibles. Also called secondary jaw. Each maxilla bears a feeler-like organ, the palpus (which discharges a gustatory or tasting function). Have two segments, the basal cardo and apical stipes . Palpus arise on a lobe of the stipes called the palpifer (five segmented). Stipes bears two lobe like structures at its apex (outer simple galea and inner jaw like structure lacinia ) Functionally maxillae are of accessory jaws, their lacinia aiding mandibles in holding the food.

99. Hypopharynx : A short tongue like structure located above the labium and between the maxillae. The ducts from salivary glands open on or near the base of hypopharynx . Labium: Lies behind the maxillae Derived by the fusion of the second pair of maxillae, hence also referred as the second maxillae.

100. Divided by transverse suture (labial suture) into two portions, basal postmentum and distal prementum Postmentum is usually divided into basal submentum and distal mentum . Prementum bears a pair of palpi called labial palpi and a group of apical lobes which constitute the ligula . Labial palpi arise on lateral lobes of the prementum called palpigers . Ligula consists of a pair of small lobes in the middle, inner glossae and outer paraglossae . Labial palpi act as sense organs comparable to the gustatory function of maxillary palpi .

101. Biting and chewing mouth parts

102. Biting and chewing mouthparts

103. Feeding mechanism : The labrum or upper lip helps the insect to pull the food into the mouth. Mandibles masticate the food. They cut off the food material. Small teeth present in each mandible work against those of the opposite for effective grinding. The maxillae aid in holding the food in mouth while it chewed by mandibles. They also aid in breaking up the food. Both maxillae and mandibles move side ways. Labial palpi works similar to that of maxillary palpi . The maxillae and labium helps in passing the food into oesophagus

104. CHEWING AND LAPPING TYPE Eg : HONEYBEES Mandibles and labrum are of chewing type and help in holding the food. But mandibles are not toothed. They are useful to crush and shape wax for comb building, ingest pollen grains. Maxillae and labium are elongated and united and formed lapping tongue. Tongue unit consists of: 2 Galea with its concaves inner surface forms a roof over the hairy glossa and fits length wise against 2 labial palps . The glossa modified into small spoon like lobe called bouton which is useful to lick the nectar. In this way a food channel is formed.

105. CHEWING AND LAPPING TYPE

106. Mode of feeding: The mandibles and labrum help in holding food / prey. In honey bees the labrum is used for molding wax into cells. Regarding intake of nectar king, Imm’s and Snodgrass gave their own view. King’s Views : After sucking the nectar with the tip of glossa , it is retracted into labial palp and galea , where the latter squeezes off the nectar which is deposited at the base of the glossa in a small cavity formed by the paraglossa . Finally as a result of bending of the labium upward, the base of the glossa comes near the mouth cavity and the accumulated nectar is sucked into the Oesophagous by the action of the pharyngeal pump.

107. SIPHONING OR NON STYLET SUCKING TYPE Order: Lepidoptera, e.g.: butterflies and moths Mandibles totally absent . Majority of Lepidoptera mandibles are wanting and maxillae to form a suctorial proboscis with the help of galea . Maxillae is composed of elongated galea . Each galea of maxillia elongated, semi-circular towards inner side. Galea of both the sides which are zippered together forming into a tubular structure, proboscis. Observe the coiled proboscis beneath the head. Liquid food (nectar) is sucked up through groove formed by galea

108. All other mouth parts highly reduced. When fully developed mouth parts, maxillary palpi are 5 or 6 segmented. Labium reduced to small ventral plate. Hypopharynx is present on floor of mouth. Feeding mechanism: When not in use, proboscis is spirally coiled and beneath the thorax. It presents an extraordinary variation in length. Eg . Sphingidae , Danaus . Proboscis extended by blood pressure. Eastham and Eassa (1955).

109. PIERCING AND SUCKING TYPE (bug type) Order : Hemiptera (4 stylet ) Mandibles and maxillae being modified to form slender bristle like stylet which rest in grooved labium. Labium project downwards from the anterior part of the head like a beak. Both pairs of stylets are hollow seta-like structures. These stylets back into prothorax (Cranston and Sprague, 1961). Mandibular stylets form anterior (outer) pair and posterior pair of stylets (inner) constitute part of maxilla. They are suited for piercing and sucking. The inner stylet are grooved on their inner faces and closely form two canals- food canal and salivary canal. Dorsal stylet as a suction canal.

110. Ventral stylet as a salivary canal. Labium no part in perforating the tissue of host plant. Its function as a protective covering for the four stylets . Hypopharynx is highly specialized in Hemiptera . Salivarium is modified into a powerful salivary pump. Feeding mechanism: At rest rostrum is flexed beneath the body. In most Hemiptera stylets are only slightly longer than the rostrum. Eg . Aphididae , Lygus . In Coccoidea stylets are forced deeper and deeper into the plant. Mandibles are first pushed then followed by maxillae. Saliva contains enzymes that can dissolve plant cell wall to penetrate down for sucking sap.

111. PIERCING AND SUCKING TYPE (Mosquito type) Order : Diptera (Female Mosquito, 6 stylet )) Mandibles, maxillae, labrum- epipharynx (food canal) and hypopharynx (salivary canal) being modified to form slender bristle like stylet which rest in grooved labium. Both the ends of maxillary and mandibular stylets are hollow saw-like structures. They are absent in male mosquito and they feed on decaying fruits. Female pierces the skin of human which it injects saliva containing an anticoagulant and an anesthetic and suck the blood. Labium does not pierce but fold up.

112. SPONGING TYPE, Eg : HOUSE FLY. The proboscis is fleshy, elbowed and projest downwards. Mandibles are absent. Maxillae are represented by a pair of maxillary palp . Labium is divided into basal rostrum, middle haustellum and distal labellar lobes. The end of the proboscis is enlarged, sponge like and two lobed which act as suction pads.they are called labella. Labella are tranversed by small channels known as pseudotrachia which collect the liquid food and open into the food channel. These insect split spit enzyme containing saliva onto solid foods to liquify them. Epipharynx and hypopharynx together form the food channel which leads to Oesophagous .

113. Mode of feeding: It is used for food which is either liquid or readily soluble in saliva. While feeding after dissolving the food by saliva, the labella is thrust into the liquid food as a result the pseudotracheae get filled with the liquid by capillary action. The food is then passed through the food channel to the Oesophagous Eg . Houseflies

114. Lacerating and sucking or rasping and sucking type Order: Thysanoptera . eg . Thrips . Labrum , labium and bases of maxillae combine and unite to form a mouth cone. Both maxillae and the left mandible are modified as stylets . Right mandible is absent. Hypopharynx reduced.

115. Thrips

116. MASK TYPE These are modified biting and chewing type. Labrum, mandibles, maxillae, hypopharynx are typically developed as in biting type of mouth parts. Labium – in the nymph this organ is modified for prehensile purpose and is known as mask. The prementum and post mentum are markedly lengthened. The ligula is undivided and represented by a median lobe which is fused with the prementum. The labial palpi are modified to form a lateral lobes each of which carries on its outer side a movable hook. These hooks which help in catching the prey. During resting period, when the insect is not feeding, the mouthparts cover a part of the head. Hence it is called mask type. Ex : Dragon fly naiads.

117. Naiad

118. DEGENERATE TYPE Eg : MAGGOTS In maggots, a definite head is always absent. The mouth parts are highly reduced and are represented one or two mouth spines or hooks.

119. DEGENERAE TYPE

120. Grasping Type Mandibles – slender, elongate, curved at their ends bearing 1-3 sharp teeth. Extreme development in males of many of the Lucanidae and Chiasognathus Maxillae – Single-lobed in lucanids called “mala” Other parts – normal Soldiers of Termites – Large, twisted, asymmetrical mandibles with peculiar “snapping action”. Some posses salivary or frontal glands (adhesive secretions). Examples : Soldier termites and stag beetles ( Lucanids )

121. Grasping Type Soldier termite

122. Mandibulosuctorial type Antlion larva

123. Mandibles and maxillae – long, exerted adopted for seizing the prey Mandibles – sickle – shaped and armed with teeth. Grooved along their ventral surface and a lobe or maxillae (perhaps lacinia ) similar in size and shape fits each groove forming a pair of imperfect suctorial tubes. Blood imbibed by means of pumping action of pharynx. Maxillary palpi – absent; labium – greatly reduced, labial palps - variable or aborted Examples : larvae of Antlions and Aphid lions, Lampyrid larvae.

124. 136 Insect Legs and their modifications “An insect usually bears three pairs of legs which are located on the ventral surface of thoracic segments . They are primary organs for running or walking , but according to the habit and habitat of insects they are modified for different purposes.”

125. 137 Structure of Insect Leg A typical leg consists of the following parts:- Coxa :- It is the basal segment and joint the leg with thorax . Trochanter :- It is the small second division of the leg which articulates with coxa but is usually fixed with femur . Femur :- It is the largest and most powerful division of the leg. Tibia :- It is the slender , usually quite long . Tarsus :- It is the fifth divisional segment and generally sub divided into 2-5 segments . The subsegment is also called tarsomere . Pretarsus :- It is the last terminal segment of the leg which represented of the leg which is represented by a complex set of claws.

126. 138

127. 139 Modifications of Leg Ambutorial or Walking Type :- It is generalized form of insect leg, which is usually adapted for walking . Example:- Cockroach and Bugs

128. 140 2. Cursorial or Running Type :- It is almost similar to walking type of leg, but it is differentiated by the tarsus which is comparatively longer and touches the ground while running. All the three pairs of leg. Example:- Ants, Blister Beetle and wasps.

129. 141 Saltatorial or Jumping Type :- Such type of legs are present in grasshopper, crickets and flea beetle where the femur of the hind leg get enlarged and accomodates the powerful tibial muscles . Example:- Hind leg of Grasshopper

130. 142 4. Scansorial or Clinging Type :- This type of legs are smaller and flat . Tibia is stout and at one side bears a thumb like process. The coxa are widely separated and tarsi bears a single claw . All the pairs of leg of louse. Example:- Head Louse

131. 143 5. Fossorial or Digging Type :- This type of legs are modified for the purpose of digging . These are powerful, broad and small in size. Tibia and tarsus short and broad with teeth like projections . Tympanum is present in fore tibia. Example:- Mole crickets and Dung rollers.

132. 144 6. Raptorial or Grasping Type :- Such legs are adapted for catching the prey and are found in fore leg of Mantids . Coxa of fore leg is more elongated whereas the trochanter is small . Tibia is spinous and fits along the femur . They are of no use in locomotion Example:- Preying Mantids

133. 145 7. Natatorial or Swimming Type :- These type legs are found in insects which lives in the water and help them to swim . The femur , tibia and tarsus of hind legs are flattened and posses the long rows of hairs . Example:- Dytiscus and Jaint water bug.

134. 146 8. Foragial or Pollen Collecting Type :- This type of legs are found in worker honey bees which is mainly adapted for carrying the pollen from the flowers. Tibia of the hind leg is dialated and covered with longs dense hairs which forms a pollen basket ( corbicula ). Pollen packer also called pollen press on tibia and tarsus. Pollen comb present on basitarsus . All the 3 pairs are modified . Example:- Hind leg of Woker Honey Bee.

135. 147 9. Stridulatorial or Sound Producing Type :- These legs are typically adapted for producing sound wherein the femur of hind leg is provided with the row of pegs on its inner side . These femoral pegs work against the outer surface of each tergum or coastal margin of the fore wing , thereby producing a sound . Example:- Male Grasshopper and cricket.

136. 148 10. Sticking Type :- In such type of legs the pretarsus is highly modified in a pair of claws and a pair of pad like structure known as pulvilli (found at the base of claws). Hollow and tubular hairs secrets a sticky substance . These are also known as Adhesive type of legs . Example:- House fly .

137. 149 11. Clasping Type :- This Such type of legs are modified for reproduction purposes . Coxa and Trochater is comparatively smaller while the Femur is thick . The tibia is slender , tarsus is one segmented and arched . This adaptation helps male to holds the female during reproduction . Fore leg of water beetle. Example:- Chleredryinus (Parasite of Sugarcane Pyrilla )

138. 150 12. Suctorial or Sucking Type :- This type of legs are also modified for the purpose of reproduction in which coxa and trochanter of fore legs are small while femur is thick and small . They are also helpful in sticking with grasses and leaves against the water flow . Example:- Male Dytiscus .

139. 151 13. Antennal Cleaning Legs :- This type of legs are modified for the purpose of cleaning antennae in which tibia possess a movable spine and the first tarsal segment with a semi-circular notch. Example:- Front legs of Honey Bees.

140. 152 14. Wax Pick Legs :- This type of legs are modified for the purpose of picking of wax plate in which Tibia possess a spine called wax pick for removing the wax plates from the ventral side of the abdomen . Example:- Middle legs of Honey Bees.

141. 153 15. Prehensile or basket like :- This type of legs are modified for the purpose of catching prey and basket forming . Example:- Dragon Flies .

142. Digestive system of insect

143. Digestive system The alimentary canal of insects is a long, muscular and tubular structure extending from mouth to anus. It is differentiated into three regions viz., Foregut, Midgut and Hindgut.

144. 1. Foregut ( Stomodeum ) It is ectodermal in origin. Anterior invagination of ectoderm forms foregut Internal cuticular lining is present. Terminal mouthparts leads into a preoral cavity. Preoral cavity between epipharynx and hypopharynx is called as Cibarium . Preoral cavity between hypopharynx and salivary duct is Salivarium . Behind the mouth a well musculated organ called Pharynx is present which pushes the food into oesophagus . Pharynx acts as a sucking pump in sap feeders.

145. 1. Foregut: Oesophagous is a narrow tube which conduct food into crop. Crop is the dilated distal part of esophagus acting as food reservoir. In bees crop is called as honey stomach where nectar conversion occurs. Proventriculus or Gizzard is the posterior part of foregut and is musculated. It is found in solid feeders and absent in fluid feeders or sap feeders. Food flow from foregut to midgut is regulated through cardial or oesophageal valve .

146. 1. Foregut: The internal cuticle of gizzard is variously modified as follows. i . Teeth like in cockroach to grind and strain food. ii. Plate like in honey bee to separate pollen grains from nectar iii.Spine like in flea to break the blood corpuscles

147. 2. Midgut ( Mesenteron ) It is endodermal in origin and also called as mesentron . This part contains no cuticular lining. Midgut is made up of three types of epithelial cells. ( i ) Secretory cells (Columnar cells) (ii) Goblet cells (aged secretory cells), (iii) Regenerative cells which replaces secretory cells.

148. Important structures present in midgut are as follows: ( i ) Peritrophic membrane (ii) Gastric caecae : (iii) Pyloric valve (iv) Filter chamber

149. Peritrophic membrane: It is the internal lining of midgut , secreted by anterior or entire layer of midgut epithelial cells. Present in solid feeders and absent in sap feeders. This layer is semipermeable in nature to digestive juices and digestion products. It lubricate and facilitate food movement. Envelops the food and protects the midgut epithelial cells against harder food particles.

150. (ii) Gastric caecae : (Enteric caecae or Hepatic caecae ) Finger like outgrowths found in anterior or posterior ends of midgut . This structure increases the functional area of midgut and shelter symbiotic bacteria in some insects. (iii) Pyloric valve: ( Proctodeal valve) Midgut opens into hindgut through pyloric valve, which regulate food flow. In certain immature stages of insects midgut is not connected to hindgut till pupation. e.g. Honey bee grub.

151. (iv) Filter chamber: It is a complex organ in which two ends of ventriculus and the begining of hind gut are enclosed in a sac. This is useful to short circuit excess water found in liquid food in homopteran insects. This process avoids dilution of digestive enzymes and concentrates food for efficient digestion. Also helps in osmoregulation by preventing dilution of haemolymph .

152. 3. Hindgut ( Proctodeum ) It is ectodermal in origin and produced by the posterior invagination of ectoderm. Internal cuticular lining is present, which is permeable to salts, ions, aminoacids and water. The main functions of hindgut are the absorption of water, salt and other useful substances from the faeces and urine . Hindgut is differentiated into three regions viz., ileum, colon and rectum. In the larva of scarabids and termites, illeum is pouch like for housing symbionts and acts as fermentation chamber. Rectum contains rectal pads helping in dehydration of faeces and it opens out through anus.

153. Gut physiology: Primary functions of the gut is to digest the ingested food and to absorb the metabolites. Digestion process is enhanced with the help of enzymes produced by digestive glands and microbes housed in special cells.

154. Digestive glands: a. Salivary glands: In Cockroach a pair of labial glands acts as salivary gland where the salivary ducts open into salivarium . In caterpillars mandibular glands are modified to secrete saliva, where the salivary glands are modified for silk production.

155. Functions of saliva: 1. To moisten and to dissolve food 2. To lubricate mouthparts 3. To add flavour to gustatory receptors 4. In cockroach the saliva contains amylase for the digestion of starch. 5. In honey bee saliva contains invertase for sucrose digestion

156. Functions of saliva: 6. In Jassid saliva contains lipase and protease for lipids and protein digestion. Jassid saliva also contains toxins which produces tissue necrosis and phytotoxemia on the plant parts. 7. In plant bug saliva contains pectinase which helps in stylet penetration and extra intestinal digestion. 8. In mosquito, saliva contains anticoagulin which prevents blood clotting. 9. In gall producing midges saliva contains Indole Acetic Acid (IAA). 10. In disease transmitting vectors the saliva paves way for the entry of pathogens

157. b. Hepatic caecae and midgut epithelial cells: It secretes most of the digestive juices. Two types of cells were involved in the enzyme secretion. Holocrine : Epithelial cells disintegrate in the process of enzyme secretion. Merocrine : Enzyme secretion occurs without cell break down.

158. C. Microbes in digestion: In the insect body few cells were housing symbiotic microorganisms called as mycetocyte . These mycetocytes aggregate to form an organ called mycetome . ( i ) Flagellate protozoa - It produces cellulase for cellulose digestion in termites and wood cockroach. (ii) Bacteria - It helps in wax digestion in wax moth. (iii) Bed bug and cockroach obtain vitamin and aminoacids from microbes.

159. C. Microbes in digestion: These microbes were transmitted between individuals through food exchange (mouth to mouth feeding) called trophallaxis and through egg called as transovarial transmission. In plant bug and ant lion grub partial digestion occurs in the host body prior to food ingestion called as extra intestinal digestion. In most of the insects digestion occurs in mid gut.

160. Absorption: In many insects absorption of nutrients occurs through microvilli of midgut epithelial cells by diffusion. Absorption of water and ions occur through rectum. In cockroach lipid absorption occurs through crop. In termites and scarabaeids (White grubs) absorption occurs through ileum. In solid feeders, resorption of water from the faeces occurs in the rectum and the faeces is expelled as pellets. In sap feeders (liquid feeders) the faeces is liquid like. The liquid faeces of homopteran bugs (aphids, mealy bugs, Scales and psyllids ) with soluble sugars and amino acids is known as honey dew, which attracts ants for feeding.

161. R espiratory S ystem of I nsects

162. All insects are aerobic organisms They get oxygen directly from environment Air is supplied directly to the tissue and haemolymph is not involved in the respiratory role. C 6 H 12 O 6 + 6O 2 6H 2 O + 6CO 2 + energy Allow oxygen to body for cellular respiration Remove carbon dioxide from cells Respiratory systems of insect are developed from ectoderm . Respiratory systems

163. Air enters into body through tiny holes spiracles U se to avoid water loss A cavity atrium or entrance is present Air passage is controlled by atrial Valves S urrounded by peritreme . Spiracles

164. E lastic in nature Cuticular pipe like apparatus Thick , helical and thread like layer taenidia give flexibility F illed with air shows silvery appearance Tracheae

165. Tracheoles The network of tracheae Diameter less than 1µm (0.2-0.3µm ) Gaseous exchange Lie within each cell Its lining not shed down on molting

166. Air-Sacs tracheae are expanded in many parts to make thin walled, collapsible structure act as air reservoir shiny white vesicle, filled with air A ssist flight by reducing gravity of insects Sound resonator of tympanic membrane H eat insulations

167. Number and Arrangement of Spiracles in Insects In the developed embryo, 12 pairs of spiracles According to number and position of spiracles, respiratory system is classified as

168. 1. Holopneustis Respiratory System 8 pairs of spiracle on first 8 abdominal segments 2 pairs found on metathorax and pro or mesothorax Example : Dipterans and some Hymenopterans 2. Hemipneustic Respiratory System : 10 pairs of spiracle present; one or two pairs are non-functional . Example: common in insect larva

169. 3. Peripneustic Respiratory System: S piracles on abdomen and prothorax open metathorax are close Example : Neuroptera , Lepidoptera, Coleoptera , Mecoptera , and Hymenoptera 4. Amphipneustic Respiratory System: Only 2 pairs of spiracles are open On prothorax Posterior abdominal segment. Example : Dipteran’s larva .

170. 5. Propneustic Respiratory System: O ne pair of prothoracic spiracle is functional. Example: most rare and found in some pupae of Diptera family. 6. Metapneustic Respiratory System: Last abdominal spiracles pair is functional . Example: 1 st larval instars of aquatic Coleopetra , Family Culicidae . 7. Apneustic Respiratory System : ( Closed circular system) All spiracles are closed R espiration takes place through gills and general body surface Example: Naiad of Mayfly, nymph of Ephemeroptera , Odonata and many endoparasites (Hymenoptera ).

171. Respiration in Aquatic Insects Appendage permits liquefy oxygen from the water Example : Larvae of mayflies and damselflies Gills are situated on lateral or posterior sides of abdomen leaf like in appearance I nsects contact with water due to fanning actions 1. Closed tracheal system Biological Gills

172. Breathing Tubes Aquatic insects submerged under the water Take oxygen directly from surface by hollow tube Siphon tube Example: Larva of mosquito 2. OPEN TRACHEAL Siphon tube

173. Few aquatic insects have bubble of air with them In diving Beetles it is prominent. C over one or more spiracle Gives short-term supply of oxygen Air Bubbles

174. Caudal breathing tube :- water scorpion Plastron :- Closely set hydrofuge hairs of epicuticle hold a thin film of air indefinitely.