Veterinary Entomology Entomology is the branch of biological science, which deals with different aspect of the phylum Arthropoda. Arthropoda word is derived from two Greek word Arthros and podos. Arthros means- jointed Podos means – foot These individuals have jointed legs. Arthropods are defined as a bilaterally symmetrical body and segmented legs bearing invertebrate animal possessing chitinous exoskeleton. Phylum- Arthropoda Out of four classes only two classes are very important for the transmission of nematodes, protozoan, rickettsia and other diseases for veterinary and medical importance and also cause other pathogenic effects.A part from this some crustacea act as intermediate host and some millipedes may be poisonous due to their stinging nature or by accidental ingestion through contaminated food and water. Class – Insecta This class includes about 70% of all the known species of animals of all kinds. The body of the insect is mainly divided into three parts i.e., head, thorax and abdomen. Head- The head is an ovoid or globular shape, composed of a number of plates or sclerites, at the anterior end of the body. The head of the insect containsOne pair of antennae Three pair of mouth parts (mandibles, upper pair jaw, Ist maxillae, maxillae is the lower pair of jaw, and labium or fused 2nd maxillae) One pair of compound eyes Three pairs of simple eyes called as ocelli. Antennae – These are pair of tactile organs having sensory hairs. The hairs are sensitive to air currents. These are situated in front of the compound eyes. Types of antennae 1. Bracycerous- when the antenna has few jointed segment. These are mostly contains 34segmented, e.g., larvae of butterfly and moth. 2. Nematocerous antenna- When the antenna contains many segments i.e., larvae of mosquitoes. 3. Pilose antenna- when the antennae joints hears very few hairs. This is present in female mosquito. 4. In case of cyclorrhapha group of flies the antenna is three segmented. The segments are called as scapes. The third segment bears a filamentus structure called as arista. The caracteristic of arista helps to identify the flies of different types. Types of arista1. Plumose on both sides up to the tip, e.g., Musca domestica. 2. Plumose only on the dorsal side with 8-10 hairs, e.g., Stomoxys fly. 3. Plumose on the dorsal side with lateral branches, e.g., Glossina fly. 4. Arista plumose on both sides up to the middle and the rest have no plumose, e. g., Sarcophaga fly. 5. Arista may not contains any plumose, e.g., Oestrus ovis fly. Eyes- There is two compound eyes present dorso-ventrally above the gena (check region). They contain large number of facets. Each facet is provided with a lens. The object is seen by the “mosaic theory of vision”. In this type of vision only a part of the object is reflected on one facet and the combined reflection and the full image the object is formed in the retina. By this way the object is visible to the insect. There are two types of compound eyes are present.

1. Dichoptic eye- here the eyes are widely apart from each other. Mostly seen in female insects. 2. Holoptic eye- here the eyes are close to each other. Mostly seen in males. Apart from these compound eyes, there are three simple eyes present and called as ocelli. These simple eyes have a single facet with a single lens. Mouth parts of insect – In insect there is three types of mouth parts found according to their feeding habit. 1. Biting and chewing type- this type of mouthpart is commonly found in lice and cockroaches. 2. Lapping and sucking type- this type of mouthpart is seen in Musca fly and also in cyclorrhapha groups of flies. 3. Piercing and sucking type- Commonly found in mosquitoes, ticks, Tabanus flies, Stomoxys flies and Glossina flies etc. The common mouth parts that are seen in insects are1. Labrum (upper lip)- This formed the upper boundary of mouth opening. 2. Labium (lower lip)- This formed the lower boundary of the mouth opening and anteriorly it is attached with one pair of labellum, which is act as tactile organs. 3. Mandibles and maxillae- each of these structures are paired in nature. These are cutting and piercing organs. These are present in between labrum and labium. 4. Epipharynx- it is a membranous structure present below the labrum or upper lip. It is fused with labrum hence, these two structures are collectively known as labrum-epipharynx. The epipharynx bears the taste organs. 5. Hypopharynx- it is a membranous structure. It is present on the dorsal side of labium. This is not fused with labium. Hypopharynx is otherwise known as tongue. The epipharynx and hypopharynx are collectively forms a tubular structure through which food passes to the intestine. Though the common insect mouthparts may contains all these parts but they differ from one insect to the other either by modification of mouth- parts or by completely absence of some of the mouthparts. Thorax- the thorax consists of three segments. Prothorax Mesothorax Metathorax Each segment bears a pair of legs. So there are three pairs of legs in adult insect. In most cases the meso and metathorax bear a pair of wings. Each segment of thorax is made up of number of chitinous plates called as sclerites. The plate that is present on the dorsal side is called tergum. The plate on the ventral side is called as sternum. The two plates on lateral sides are called as pleuron plates. Tergum- it is present on dorsal side of thorax. It is otherwise called as notum. It is further divided into four different portions. Prescutum Scutum Scutellum Post scutellum Parts of thorax-

Leg- In case of class insecta there is three pairs of legs. In case of class Arachnida, there is four pair of legs. The leg is divided into a number of segments. Each segment is called as podomere. There are usually five segments present. These segments areCoxa, trochanter, femur, tibia and tarsus or (CTFTT). The tarsus is divided into 3-5 segments and the last segment of the tarsus has a pair of claws. In between the claws there is a spine like structure called as empodium. Below the claws there is a pair of soft pad like structure known as pulvillus. Wings- In case of insects there are two pairs of wings present. One pair on mesothrorax and other pairs are on metathrorax. Some time there are some modifications, e.g., In case of diptera, the insects have one pair of wings on mesothorax. The 2nd pair of wings or metathoracic pair of wings modifies into knob like structure called as Halters or balancers. They help during flying. In case of beetles the mesothroracic pairs of wings are hard and chitinous. They do not help in flying. They only remain as a protective covering over the metathoracic pair of wings. These hard wings are known as elytra (in Coleoptera). The wings develop during pupal stage. These contain breathing tubes, which are commonly termed as wing veins. Morphology of the wings- Each wing has- two borders, three margin and three angles. The anterior portion of the wing is known as costal border and the posterior par or border of the wing is known as ventral border. The portion of the wing that aways from the body is known as apex. The angle between anterior body and costal margin is called as costal angle. The angle between costal margin and apical margin is called as apical angle. The angle formed by posterior margin and posterior part of the body is called as anal angle. At the base of wings on the posterior border in some insects there are a large number of lobes towards the posterior borders. These are termed as-squama, antisqama, aluta and anal lobe or SAAA. Wing venation- they are cuticular out growth which contains veins, which are breathing tubes or trachea. Different insects have different types of wing venations i.e., the wing veins are arranged in different insects in different manner but there is a common pattern of wing venation in which the wing veins are named and their branching are situated. Wing veins are named and their branching are situated. Wing venation can be studied by two methods. 1. Comstock Needham‟s system (RCN system)- There are six main or large wing veins. The main wing veins are present in the basal half of the wing. These veins areCostal vein Medial vein Subcostal vein Cubital vein Radial vein Anal vein The costal and subcostal veins are unbranched. Radial, medial and some time cubital vein may be divided into four branches. Anal vein is divided into two branches. In some insects the last four veins may not have any branches or in some cases only few branches are present or some times a complete vein may be absent.

At the anterior margin of the wing there is a vein called costa. Below this there is another vein subcosta. The radial vein is divided into two main branches the first one is R1and second one is R2. The R2 is nd these names are given to those veins that are present in the apical half of the wing. The vein that is present immediately below the subcostals known as first longitudinal vein and next to it is the second longitudinal vein and like wise the number are given. Apart from these longitudinal veins there are some crossed veins which join with the longitudinal veins producing or forming some areas which are known as cells. The name of the cells is given according to the vein that is present anterior to the cell. Some cells may not be surrounded by vein from all the sides called open cells and those, which are surrounded by the veins called as closed cells. Abdomen- this consists of 10-11segments out of which some time or many times only eight segments are visible due to the fusion between the segments. The abdomen is a long tube like structure. Each abdomenal segment has two spiracles, which are also known as stigmata. Through these spiracles the insects respire. In case of males the last three abdominal segments are modified into male genital organ known as hypogium and in case of females the last abdominal segment is very small and becomes telescopic to form the ovipositor which helps in depositing the eggs or the larvae according to their will. The abdomen has various stripes colour bands and some hairs or bristles. The study of hair or bristles on the abdomen is known as chaetotary. Internal structure - Just below the exoskeleton transverse muscle fibres is present. At the anterior part these muscles are responsible for the functioning of the mouthparts, locomotory organs such as wing and legs, respiration etc. Below the muscle fibers the body cavity is present which is known as haemocoel. This contains all the internal system such as the digestive systems, respiratory, circulatory, excretory, nervous and reproductive system. Digestive system- the alimentary canal is divided into three parts. Foregut or fore intestine or stomodaeum Midgut or mesenteron Hindgut or proctodaeum Stomodaeum and proctodaeum are ectodermal in origin and it also covered external part of the body but the midgut or mesenteron is endodermal on origin. The midgut or the mesenteron is the true stomach where digestion of food materials takes place. In the hindgut the first potion is a ring of malpighian tubules which are present at the junction of the midgut and hindgut. These tubules are responsible for collecting the waste materials from the surrounding body cavity and expel them into hindgut. The hindgut cosists of small intestine, large intestine, rectum, anus and a number of rectal papillae. In cycorrhapha group of insects the midgut and hindgut are lined by a thin delicate and chitinous membrane, known as the peritrophic membrane. This membrane is permeable in nature and food materials are absorbed through the membrane. The second layer of this membrane is also protects the epithelial cells from injury by the food materials. It is closed attached in the anterior part of the midgut and hangs loosely in the hindgut. Circulatory system- Although there is no definite blood vescular system in case of insects. The circulatory system consists of a heart and aorta. The heart is tubular in nature and is divided into several compartments. Each compartment has two opening known as ostia and in between these

compartment there are valves. The heart is surrounded by pericardium, which is sac like structure. Blood enters into the pericardium and through the ostia they reach into the heart and pump away through the ostia. The aorta supplies blood to other organs in the body cavity all organs are bathed with the blood. The blood of insect is known as haemolymph and colour of this may differs from insect to insect due to the present of some pigments. In case of larvae of Chironomus dorsalis the blood contains haemoglobin and is red in colour hence these larvae are sometimes known as “blood worm”. Respiratory system- The respiratory system consists of branching tube which are3 made up of chitin. These tubes are known as trachea and they ramify or branch in the body of the insects and end in small branches. The trachea opens to out sides at the sides of the body and these openings are known as spiracles or stigma. Spiracle lined by a chitinous plate known as peritrema. This chitinous plate may also contain some hairs, which control inflow of air into the spiracles. The number and position of the spiracles may be different in different types of insects and also in their developing stages of insect such as larvae. According to the position of spiracle the larvae of insects may be divided into different types. 1. Holopneustic larvae- In this case spiracles are present on the meso, metathorax and in all the abdominal segment e.g., Hymenoptera (bee). 2. Peripneustic larvae- In this case spiracles are present in the prothrorax and in all the abdominal segment e.g., Catterpiller (larvae of butterfly). 3. Amphipneustic larvae- Spiracles are present on lthe prothorax and only on the last abdominal segment e.g., 2nd and 3rd stage larvae of Musca and Stomoxys. 4. Propneustic larvae- In this case spiracles are present only on the prothorax e.g., larvae of mosquitoes belonging to the genera Anopheles, Culex, Aedes and Mansonia. 5. Metapneustic larvae- Spiracles are present only on last abdominal segment e.g., 1st stage larvae of Musca and Stomoxys. 6. Apneustic larvae – Spiracles are absent on the segment of the body e.g., the larvae of some aquatic insects which respires through the skin. Nervous system- In the nervous system there is a supra oesophageal ganglia. This is present on the dorsal side of oesophagus and it supplies nerve fibres to the brain. Below this supra oesophageal ganglia there is sub-oesophageal ganglia. These two are connected by transverse oesophageal commissure. From this sub oesophageal ganglia the nerve trunk or nerve fibres run down words and this join with the ganglia of the abdominal and thoracic segment. From this ganglia nerves fibbers arise and supply to the different organ of the body. Reproductive system- the males and female are found separately. The male reproductive system is known as Hypopygium. It consists of two testes, from which vas efferent arise and joins together and form the vas deferens in which there is dilated portion known as seminal vesicle. Seminal vesicle is followed by an ejaculatory duct, which opens into the penis. This male reproductive system also consists of a pair of accessory glands. The female reproductive system consists of a pair of ovaries which is divided into number of compartment and each compartment is known as ovariole from each ovary an oviduct arises which joins together and continues as the uterus and ends in vagina. In most insects one ovipositor is present. The female reproductive system also has some accessory glands.

Development of insects- Usually lay eggs but some insects are larviparous in nature and they deposited the larvae e.g., Glossina species, Sarcophaga species, Oestrus ovis etc. In the development of insects, the larvae usually moult three times resulting in four stages. Each stage that results after a moult is known as „instar‟. The period between two moults is known as stadium. After the third moult of skin of the larvae is may or may not cast off and remains as a protective covering over the 3rd stage larvae which later becomes hard and is known as puperium. After the third moult the larvae develop into pupa in case of fly and mosquitoes. But in case of lice, ticks and mites, pupa stage is known as nymph. The young arthropods that comes out from the puperium is known as imago which develops commonly known as maggots and the cast of skin after the moult is known as exuviae. Moulting- It is a process of casting of the exoskeleton and development of new exoskeleton in place of it. During this process the exoskeleton also cover the entire body and, lining of the fore gut or the stomodaeum, hind gut, respiratory trachea and outer body covering, it also cast off and new lining are produced. They are ectodermal in origin. Metamorphosis- It is a proces in which there is change of form i.e. associated with each moulting during development of insect that means often each moult the insect change in form. This change is known as metamorphosis. It is of three types1. Ametamorphosis or ametabolous- In this case there is no change of form i.e., the stage that comes out from the egg completely resemble with the adult one e.g., silverfish insect. 2. Imcomplete metamorphosis or hemimetabolous- this type of development is mostly seen in lice, tick, mite, bedbug and cockroach. In this case the form results after each moult partially resemble with each other or sometimes greatly resemble, sometime they only different between the young and adult one are the genital organ and the wings. The stage that comes from the egg is known as the larva, which moults to 1st stage nymph- 2nd stage nymph- 3rd stage nymph – Adult. 2. Complete metamorphosis or holometabolous- In this case there is complete change of form between the stages that result after each moult. Hence different names are given to each stage e.g. egg- larva- pupa – Imago. Each stage is completely different from the other one e.g., Dipterous fly- mosquitoes, butterfly etc. Types of larva- there are different types of larvae according to the development of head and mouthparts and legs. 1. Eucephalous larvae- they have got well-developed head and welldeveloped masticatory mouth parts e.g., larvae of mosquitoes, Chironomus dorsalis and Phlebotomus species of fly. 2. Hemicephalous- In this case there is not well developed head but masticatory mouth parts are present e.g., larvae of Musca, Stomoxys, Tabanus, calliphora group of flies. 3. Acephalous- In this case both head and masticatory mouthparts are not developed e.g., Glossina sp., Melophagus ovinus. 4. Polypod- In this case there are three pairs of legs on the thoracic segments and also there are some false legs that are known as prolegs which are present on abdominal segments e.g., larvae of butterflies. 5. Oligopod- In this case legs are only present on thoracic segment e.g., larvae of the beetles.

6. Apodous- In this case legs are completely absent on both thoracic and abdominal segments e.g., larvae of flies and mosquitoes. Types of pupa1. Free or exarate- these pupae are very much active, they move freely because their legs and wings are not bound by the molting fluid e.g., pupae of beetles. 2. Obtectate pupae – In this case though the moulting fluid bound the legs and wings but there is some movement of pupa. The cast skin of the 3 rd larvae stage do not remain attach with the pupa as puparium hence there is some movement of pupa e.g., mosquitoes, butterfly, Tabanus and Simulium sp. 3. Coarctate pupae- In this case the cast skins of the 3rd lavae stage remains attached with the body of the pupa as puperium and pupa remains inside the puparium and it can not move freely e.g., the pupa of Musca, Stomoxys, Oestrus fly, Hypoderma etc. Imago- It is the young insect that comes out from puparium either by making a „T‟ shaped opening or circular opening at one end of the puparium. Harms caused by insects1. Annoyance and worry- the biting and siting of insects cause discomfort and worry to the animals due to this the animal swing their tail and stamp their feet. They do not get proper rest and become off feed. Due to this there is loss of condition, sometime due to they attach of some flies such as Hypoderma and Oestrus species the animal become terrified and they run here and there and make injury themselves. Most of the flies cause worry and annoyance to the animal e.g., mosquito, tick, and fly. 2. Direct injury-The stings of bees and wasps and sometime the stings of scorpions cause direct injury on the skin of the animal. They produce very painful swelling on the skin. 3. Dermatosis – The lice and mites directly attach on the skin and cause thickening and wrinkling of the skin and there is loss of hair or wool. 4. Myiasis- It is a condition caused by invasion of dipterous fly larvae in living tissue of animals. This is also known as maggoted wound e.g., by Tabanus and Stomoxys. 5. Setiasis- this is a similar condition like myiasis but thi is caused by Lepidopterous fly larvae in the living tissue of animal resulting in irritation and injury. 6. Anaemia and loss of condition- the tick and some blood sucking fly or arthropods e.g., Tabanus are voracious blood suckers and when they are found in large number in animal body they cause severe anaemia and loss of condition. 7. Disease transmission- a large number of bacterial, viral, rickettsia, helminthes and protozoan disease are transmitted by insect. These diseases produce a great loss to the livestock industries. The transmission of disease takes place by mainly two methods. a. Mechanical transmission- In this case the disease producing organism remain in the mothparts or proboscis of the insects they do not under go any chang or development but are directly transmitted from animal to animal while biting and sucking blood e.g., Trypanosoma evansi. b. Biological or cyclical transmission- It is three typesi. Propagative transmission- In this case the disease producing agent multiply inside the body of insect before they are transmitted to

ii.

iii.

another host e.g., number of bacterial diseases are transmitted by fly and flea. Cyclodevelopmental transmission- in this case the diseaseproducing organism develops into the infective stage inside the insect body before being transmitted to another host e.g., the filarial worm transmitted by mosquito. Cyclo-propagation- In this the organisms both multiply and devoloped into the infective stage inside the insect body before they are transmitted to the new host e.g., Babesia species transmitted by ticks, malaria parasite transmitted by mosquito.

Classification of class insecta Class- Insecta

Subclass 1. Apterygota- these are primarily wingless insects and metamorphosis is completely absent or very slight. Subclass 2. Pterygota- Wings are primarily present but they may be absent or reduced during the adult stage or during other stage of development or metamorphosis is variable i.e. it may be holometabolous or hemimetabolous. Pterygota is again divided into two divisions. Division a. Exopterygota- the different are in the exopterygota the wings develops externally as buds and the metamorphosis, simple, incoplete and rearly pupal stage found or hatch from eggs into adult without pupal period. The immature stages usually resemble with adult in structure and habit. a. Exopterygota (wings are develop externally) i. Wings can be folded when no in use, can crowl like wing less form e.g., Locust, Cricket, Mantis etc. ii. Wings can not be folded, good fliers, predator insects and ancient group e.g., Dragonfly. Exopterygota further divided into ten orders these are as follows1. Orthoptera- e.g. grasshopper and cockroach 2. Dermaptera-e.g. earwings 3. Isoptera- e.g. ant, termite. 4. Plecoptera- e.g. stone flies 5. Siphunculata (syn. Anoplura)- sucking lice families are i. pediculidae e.g. pediculus, phthirus pubis ii. Haemtopinidae e.g. Haematopinus iii. Linognatidae e.g. Linoghatha. 6. Hemiptera – it has two families i. cimicidae e.g. Cimex and ii. Reduviidae e.g. Reduviid and Tritoma bugs. 7. Psocoptes e.g. book lice, bark lice 8. Odonato- e.g. dragon fly 9. Mallophaga (biting lice)- it divided into two sub orders i. Amblycera e.g. Menopon, Menacanthus etc. ii. Ischnocera e.g. Goniodes, Damalina, Goniocotes etc. 10. Thysanopter e.g. thrips

b. Endopterygota- Wings developed from inside of the body and metamorphosis is complete. wings are developed internally. They are holometabolous and pupal is always present. This division is divided into following orders1. Coleoptera e.g., beetles 2. Hymenoptera e.g., bees and wasps 3. Lepidoptera e.g., butterfly and moth 4. Siphonaptera or Aphaniptera e.g., fleas 5. Diptera e.g., true flies (mosquito, housefly, sandfly etc.) 6. Neuroptera e.g., lace wings

stage

1. Order Diptera – this order is divided into two suborers. The insects belonging to this order have only one pair of wings on the mesothorax. The metathorax pair of wings are modified into knob like structure known as balancers or halters. This order is divided into two suborders – a. suborder 1. Orthorrhapha b. suborder 2. Cyclorrhapha a. suborder 1. Orthorrhapha- Larvae are eucephalus. The puae obtectate and the imago comes out from the puparium by making a “T” shaped opening on the dorsal side of the puparium. It is divided into two series i. Nematocera and ii. Brachycera. i. Nematocera- The antennae are many segmented. The maxillary palp is 4-5 segmented and the third long vein in the wings is never forked or divided e.g. mosquitoes. Nematocera further divided into seven families, these are as follows1. Psychodidae- e.g Phlebotomus 2. Simulidae – e.g. Simulium (black fly) 3. Tipulidae e.g. (daddy – long legs crane flies) 4. Chironomidae e.g. chironomus 5. Biolonidae e.g. non biting medges 6. Ceratopogonidae-e.g. culicoides (biting medges) 7. Culicidae i. sub family- culicinae e.g Culex, Aedes, Mansonia ii. sub family- Anophelinae e.g. Anopheles ii. Brachycera- The antennae are 3-4 segment, the palp are two segments and the 2nd long vein is not divided. This series brachycera is divided into only one family Tabanidae. Tabanidae family divided into two sub families‟ i. tabaninae- e.g. Tabanus fly, Haematopota etc. ii. Pagoninae-e.g. Pangonia, Chrysops etc. b. Sub order 2. Cyclorrhapha- Larvae are hemicephalous, the pupae are coarctate and imago comes out of the puparium from a circular opening at one end. The cyclorrhapha suborder is divided into five families1. Anthomydae e.g. Tabanus, Stomoxys, Glossina etc. 2. Tachinidae- this family divided into two subfamilies i. sarcophaginae e.g. Sarcophaga and ii. Caliphorinae e.g. Caliphora. 3. Oestridae e.g. Oestrus, Hypoderma etc. 4. Gasterophilidae e.g. Gasterophilus. 5. Hippoboscidae e.g. Hippobosca, Melanophaga. Or Suborder Cyclorrhapha can be divided into three seriesseries1. Aschiza

series2. Schizophora- it is further divided into two sub series i. Calyptera e.g. Musca, Stomoxys etc. and ii. Acalyptera has the family Gasterophilidae e.g. Gasterophilus. Series3. Pupirara (larviparous) this series has the family Hippoboscidae e.g. Hippobosca, Melaphagus, Pseudolynchia etc. Family 1. Psychodidae This family has the genera Phlebotomus and Sergentomyia, some species of the genera arePhlebotomus argentipes, P. sergenti, P. major, P. papatasii and Sergentomyia babu. Common name of this insects are “sand fly”or sometime known as owl midges.