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and thus reduce drag during flight. They also insulate the insect against cold. Scales

and their colour also help in camouflage, mimicry and in seeking mates. In many

small butterflies, the flight is of zig-zag type and thus helps in attaining high lift

in a gradual fashion. Some moths are nocturnal fliers and hence highly specialized.

Metamorphosis is complete. Two pairs of large wings are present. Some moths are

known for echolocation and for escaping from predatory bats during flight.

Examples: Butterflies, moths, silk moths and Monarch butterfly.

Coleoptera

In most species of beetles, the forewings are heavily sclerotized (hardened) and

thick and are known as elytra (singular elytron). In Coleoptera, the forewings act as

parachuting devices and contribute to lift. The hindwings are membranous, resilient

and longer than the elytra, folded longitudinally and transversely under the elytra,

which protect the delicate hindwings when at rest (Fig. 5.10a). The elytra tend to

cover the hind part of the body and protect the delicate hindwings. The elytra are

connected to the pterothorax. The elytra must be raised and maintained in a horizontal

position in order to move the hindwings and maintain lift during flight.

A beetle’s flight wings are crossed with veins and are folded after landing and

are covered below the elytra (Fig. 5.10b). In some ground beetles and in weevils,

the ability to fly has been lost secondarily, and hence, they have the two elytra fused

together, forming a shield over the delicate abdomen. The wings are rotated forward

on their base into flight position. This action spreads the wings as they unfold their

wings horizontally. There is a spring mechanism in the wing structure. The wing

venation is reduced and modified due to its folded nature. In glow-worms, both the

Fig. 5.10 a Elytra spread out and b Elytra closing the abdomen