Division ENDOPTERYGOTA (=HOLOMETABOLA)
(Dr. Girish Chandra)
(Beetles and weevils)
This is the largest of insect orders having over 300,000 species in the world. They are minute to large insects, possessing heavily sclerotized bodies. Compound eyes well developed but ocelli lacking. Antennae 9-11 segmented. Mouth parts strong biting and chewing type. Fore wings heavily sclerotized, forming elytra that meet on the midline. Hind wings membranous with reduced venation and they are kept folded under the elytra. Legs variously adapted, with 4-5 segmented tarsi. Cerci are absent. In weevils head is produced into a long snout, with mandibulate mouth parts for boring into seeds. Beetles are polyphagous or sometimes predaceous, found in a variety of habitats. Their larvae are called grubs, which mostly develop in soil.
They are collected by sweeping with net or by beating tray. Many species are found under the stones and logs and can be picked up by forceps. Pinning is done through the anterior one-third of the right elytron. For larger species abdomen is slit on the ventral side and viscera removed.
They are tiny insects having 300 species which are parasitic on hoppers and bees. They exhibit sexual dimorphism.
Male: Small, measuring about one mm. Fore wing reduced but hind wings large, membranous, fan like. Mouth parts are vestigial, compound eyes are large, with few large ommatidia. Ocelli absent. Legs long with fore and middle coxae elongated.
Female: It is wingless, incompletely developed, without appendages, parasitic and spends the entire life inside the host abdomen. Head and thorax fused and abdomen enormously enlarged. Viviparous. Larvae are called Triungulin, which possess well developed eyes, antennae and legs. They crawl out through the genital opening and find a new host and penetrate into it through the intersegmental membrane. Then retrogressive metamorphosis takes place and the triungulin loses appendages and eyes, which are regained only in the case of male after the last moult. Male mates with the female that continues to live in the host abdomen through its genital opening and then dies in a day.
Stylopids are obtained by collecting infected hosts and dissecting the female out or by rearing the adults by holding the host in a cage. All stages are mounted on slide.
(Lace wings and Ant lions)
There are about 4000 species in this order, which includes small to medium sized insects with slender bodies and prognathous head. Wings are narrow at base and broader at the tip, membranous, transparent and having net-like venation but the front margin of fore wings is not bend inwards as in dragon flies. When folded, wings are held over the abdomen in a roof-like fashion. Antennae are long and clavate, which readily differentiates them from dragonflies and damselflies. Compound eyes are large and three ocelli are also present. Mouth parts are strong biting and chewing type adapted for predatory life. Legs are short and slender with 5-segmented tarsi. Abdomen slender without cerci.
Both adults and larvae of lace wings are predaceous on aphids and hoppers and thus help in biological control of these pests. Ant lion larvae make funnel-like sand traps in which crawling insects like ants are trapped and dragged under the sand by the larva which lies in wait under the sand funnel. Larvae can be collected with forceps and preserved in alcohol and adults can be collected with net and pinned through thorax. Smaller individuals should be mounted on card triangle.
(Scorpion flies and Panorpids)
This order includes 500 species of small to medium sized, slender-bodied insects having hypognathous head that is elongated into a beak form and having strong biting and chewing type of mouth parts. Compound eyes are large and ocelli present or absent. Antennae are long and filiform. Wings are long and membranous, held folded over the abdomen at rest. Legs are long and slender, with 5-segmented tarsi. Hind legs have prehensile tarsi which are used for capturing prey. Abdomen of male is curved upward like the sting of a scorpion (hence the name scorpion flies) but in female it is straight. Cerci are short.
They are collected with net and pinned through thorax.
There are 3600 species in this order. They are medium-sized, cryptically coloured insects with soft bodies, hypognathous head, large compound eyes and long filiform antennae. Wings are covered with hairs and fore wings are larger; otherwise they look like small moths. Mouthparts are poorly developed mandibulate. Legs are long and slender, with 5-segmented tarsi. Abdomen bears 1or 2-segmented cerci. Adults feed on nectar and are short-lived.
Larvae are aquatic and construct cases around their bodies by secreting silk to which sand particles and debris are attached. Larvae can be collected from water by handpicking or with aquatic nets and can be kept in aquarium for adult rearing or they can be preserved in alcohol. Adults can be pinned and stretched like Lepidoptera.
(Butterflies and moths)
This is a large group containing over 105,000 species of minute to very large soft bodied insects. Wings and legs covered with pigmented scales. Head is hypognathous with large compound eyes and mouth parts forming long, coiled proboscis for sucking nectar from flowers. Maxillae and mandibles are vestigial. Legs have large coxae and 5-segmented tarsi.
Butterflies are diurnal and keep their wings folded vertically over the abdomen when at rest. Their antennae are clavate and they are mostly brightly coloured insects having slow and dodging awkward flight. Mimicry is a common phenomenon in butterflies.
Moths are mostly nocturnal and dull coloured insects showing protective colouration. They camouflage very well on tree trunks and some species that rest in hidden situations possess frightening colouration or eye spots. Moths have filiform or pectinate antennae, large bodies and wings are not as broad as in butterflies. They keep their wings stretched horizontally when at rest, which helps them in camouflage against the background.
Larvae are called caterpillars, which are mostly phytophagous and hence noxious pests. They should be preserved in alcohol. Adults can be collected by netting. A strong killing bottle should be used to avoid agitation by the insect, which may damage the wings. In large insects thorax should be pinched from sides to break flight muscles before putting them in killing bottle. Wings should not be touched as the scales come off easily wiping the colour. They should not be left in the killing bottle for long period. They should be pinned through thorax and wings fully stretched.
(Bees, wasps, ants and sawflies)
This is a large group of hard-bodied, medium sized insects containing over 120,000 species in world. Head is hypognathous, with large compound eyes and 3 ocelli. Mouth parts strong mandibulate type but in honey bees lapping and chewing type. Wings are membranous, transparent with specialized venation. Wings may be absent in some as in ants. Legs slim, long but strong having 5-segmented tarsi. Abdomen with a thin petiole, except in saw flies. Female with a prominent egg-laying device called ovipositor.
They are parasitic, predators or phytophagous or nectar feeders. Social life is well developed in ants, honey bees and wasps. Pupa either naked or in silken cocoon. They are collected by net and pinned through thorax. Venomous species should be guided into the killing bottle which has to be taken inside the net.
(Flies, mosquitoes, midges, sand flies, gnats)
This is a very diverse group containing about 75,000 species of small sized insects. Fore wings are well-developed and membranous while hind wings are reduced to stub-like halteres or balancers. Compound eyes are large, covering major portion of the head. Ocelli are either three or none. Antennae are variable, setigerous or aristate in flies and plumose in mosquitoes and sand flies. Mouthparts are sponging type, haustellate in flies and piercing and sucking type in mosquitoes, horse flies and sand flies. Larvae are called maggots, which are terrestrial, aquatic, parasitic or phytophagous.
They are very diverse insects and therefore can be collected by all methods. Net can be used for fast flying species and aspirator or small ones. Asilidae can be collected by dropping a net over them. Baits can be used for flies. They are pinned through thorax and wings stretched. Mosquitoes and sand flies can be mounted on slides. Larvae are killed in hot water and preserved in alcohol.
This order consists of 1000 species of fleas, which are all parasitic on birds and mammals and have small, compressed and highly sclerotized dark bodies. Head is hypognathous with spines and sometimes with comb. Compound eyes are reduced and ocelli absent. Antennae are pectinate, short and concealed in a groove. Mouth parts are piercing and sucking type. They are secondarily wingless insects having small thorax that is closely united with the thorax. Legs are long and strong, hind legs being the longest, modified for jumping. Claws adapted for clinging. Body covered with orderly rows of spines. They are vectors of plague.
They can be collected by killing the host in a bag of linen cloth and then picked by wet brush, preserved in alcohol and mounted on slide. Dark specimens should be boiled in 10% KOH, then washed thoroughly in water, dehydrated and mounted in canada balsam on slide.