EXOPTERYGOTA


Division EXOPTERYGOTA (=HEMIMETABOLA)

Order EPHEMEROPTERA

(Ephemeral=short-lived)

(Ex. – Mayflies, Dayflies and Shadflies)

They are small, light-coloured, soft-bodies, light greenish or yellowish insects. Head is prognathous and compound eyes well-developed. Ocelli three. Short, setiform antennae. Mouthparts biting and chewing type by vestigial. Weak clinging type of legs, with 5-jointed tarsi. Tip of abdomen with two or three long cerci. Larvae are aquatic and called “Naiad”, having abdominal gills, chewing mouthparts. Larvae are mostly herbivorous but sometimes carnivorous also.

Adults are found in swarms, particularly in the morning and evening, near water bodies. They can be collected by net or caught at light, can be preserved in alcohol or mounted on card-point. Larvae can be collected by dragging a net through weeds in water and preserved in alcohol.   

Order ODONATA 

 (Odonus=toothed) 

(Dragonflies and damselflies)

Medium to large-sized insects, with well-sclerotized, hard bodies, hypognathous head, large compound eyes and 3 ocelli. Antennae are short, 3-segmented, aristate. Mouthparts are strong biting and chewing type. Wing venation is net-like, with large number of cross veins. Larvae are aquatic and called Naiads and are predaceous on small insects and other organisms.  

Dragonflies have stout bodies, large eyes, which almost touch each other; bases of wings are broader than the apical part; wings are held horizontally while at rest. They are strong fliers and catch their prey in flight. Normally fly high in the open air.   

Damselflies possess slender bodies and small head; their eyes are smaller and widely separated from each other. Wings are narrower at the base and broader towards the apex; venation net-like. They usually spend time under the canopy of the plants, are not very strong flier and hunt small insects that are feeding on the plants. 

Odonata can be caught by net having long handle, killed and pinned. Some bigger and fast-flying species are difficult to catch and have to be shot with cartridges filled with dust. In pinned specimens abdomen breaks easily and to avoid that an incision should be made on the ventral side of the abdomen and the intestine removed. 

Order Orthoptera  

(Orthos=straight; pteron =wing)  

(Grasshoppers, locusts, crickets, mole-crickets)

Medium to large sized insects, having long, jumping hind legs. Fore wings thick and leathery in texture and cover the larger, membranous hind wings which are used for flying. Fore wings are used as balancers during flight. They have large compound eyes and 2-3 ocelli. Mouth parts are strong biting and chewing type. In crickets, particularly in mole-crickets, fore legs are modified for digging and hind legs for jumping. 

They are caught by dropping a net over them when they are resting and keeping the frame tightly pressed down. They can also be collected by sweeping the grasses with a net. Crickets can easily be detected by their songs and can be collected by digging their burrows. They are pinned through the thorax. In large specimens abdomen should be emptied by slitting on the ventral side. 

Order DICTYOPTERA

(Dictyos=net; pteron=wing)

(Cockroach; Praying Mantis)

Medium to large insects, with forewings leathery or chitinous, tegmen-like and hind wings large and membranous used for flying. Head is hypognathous, with strong mandibulate mouth parts. Eggs are laid in a protective ootheca. 

Cockroaches have dorso-ventrally flattened, oval body, with a large exposed pronotum and a small head. Ocelli either 2 or none. Antennae very long and setaceous, generally longer than body. Legs similar in structure and adapted for running. They usually have dark colours and characteristic odor. They are found in dark and damp places and are omnivorous and scavengers in habit. 

Praying mantis has elongated, cylindrical body, generally matching the background. Prothorax is elongated like a neck and head is mobile having filiform antennae that is shorter than the body. Ocelli 3 or none. Fore legs are raptorial with long spines, modified for capturing and grasping prey. Middle and hind legs are adapted for slow-walking. They ambush their prey and eat it alive.  

They can be collected by net or in pit-fall traps or by searching under stones, logs, gutters or any other hidden habitat. They are mounted on pins. Abdomen of larger specimens should be emptied by slitting it on the ventral side and drawing out the contents. Mantids are protectively coloured insects and therefore can be effectively collected by hitting the bushes with a stick over a white sheet.  

Order PHASMIDA

(Phasmidus=ghost or spectre)

(Leaf insects and stick insects)

They are cryptically coloured, brown or green phytophagous insects. Fore wings are leathery while hind wings membranous. Mouthparts are biting and chewing type. All legs are similar with small coxae and used for slow walking on plants. Head having long filiform antennae and small compound eyes. Male genitalia and ovipositor concealed. 

Leaf insects are superb mimics of the broad-leaved plants. Their wings are flattened, green and venation mimicking leaf-venation. Legs also got flattened leaf-like. They are impossible to locate on the plants as the entire body is perfectly camouflaged. Their movements are slow.  

Stick insects mimic grasses. Their bodies are elongated like strands of grass. Legs and antennae are thin and long. They feed on grasses perfectly camouflaged and sometimes sway as if in breeze.  Phasmida are difficult to notice and therefore best collected by sweeping through the grasses by a net or by beating the plants with a stick over a white sheet. They are pinned though the thorax and preserved dry.        

Order PLECOPTERA

(plekein=to fold; pteron=wing)

(Stoneflies; Salmon flies)

They are medium to large insects, having about 1500 species. Head is prognathous, with small to moderate compound eyes. Ocelli present or absent. Antennae long, either filiform or setaceous. Mouthparts are mandibulate but weak. Wings are transparent, the hind wing a little broader, while resting they are folded over the abdomen. Tarsi 2-3 segmented. Tip of abdomen with two long filiform cerci but without an ovipositor. Males can produce drumming sound with a disc-like percussion on 9th abdominal segment. Adults are herbivorous or predaceous found resting on vegetation by the side of water sources. Nymphs are aquatic, predaceous, found in the rapidly flowing streams. 

Adults can be collected by sweeping through waterside vegetation. Nymphs can be caught by water-nets or with underwater light traps. Adults can be pinned but nymphs, being soft bodies, should be preserved in alcohol. 

Order ISOPTERA

(isos=equal; pteron=wing)

(ex. – Termites)

They are small (2-3 mm long) soft-bodied social insects having caste system. The castes are queen, which is physogastric (having enormously enlarged abdomen), males which are apterous in the nest and alate during nuptial flight; workers having broad, chewing type of mandibles; soldiers having long, pointed dagger-like mandibles for defence and in some colonies there are nasutes which bear a long pointed snout for secretion of a highly corrosive fluid that can be used to defend the colony or to make galleries through hard rocks.

They are photophobous and live in underground nests called “termatoria” and always move through galleries. Compound eyes are small or sometimes absent; ocelli also either two or absent. Head is prognathous and antennae moniliform. Mouthparts are mandibulate type. Abdomen is broadly attached to the thorax. Legs are short adapted for slow-walking and tarsi 4-jointed. Wings when present are of equal size. 

Termites, commonly called white-ants, live in underground nests, over which they may make huge termite mounds for maintaining the nest temperature. Some species also live in earthen galleries on the trees. During breeding season termites produce a large number of male and female winged forms, which come out of the nests and take to nuptial flight, where mating takes place, after which they shed their wings and crawl on the ground in search of a new nesting site.

They excavate a small gallery and lay their first batch of eggs which all hatch into workers which keep enlarging the nest. Once the nest is completed, the queen settles in the royal chamber and starts enlarging her abdomen and reproductive organs, after which her only job remains to lay eggs. She lays about 30,000 eggs per day and survives to do this duty for about 30 years. Nuptial flight is the only way these subterranean creatures can disperse to long distances. 

Order ZORAPTERA

(zoros=purely; aptera=wingless)

(Only one genus Zorotypus containing 20 species)

They are small, pale, soft bodied insects resembling termites, with large hypognathous head. Antennae moniliform, 9-segmented and the size of the segments increases gradually from base to the apex. Mouthparts biting and chewing type. They are mostly without eyes and Ocelli but some species have eyes. Legs are short and adapted for slow walking, with 2-segmented tarsi. Cerci are short. They are gregarious insects but do not display caste system. They feed on fungus and some are predaceous on mites. 

Zorapterans are found in decaying wood or under the bark or in humus and can be collected by aspirator or extracted with Berlese funnel. They are soft bodied and therefore should be preserved in alcohol and mounted on slide.

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