1

Introduction

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and recognize targets. ‘Optic flow’ is the apparent movement of texture in the

visual field during flight. Some principles of visual guidance (optical flow)

may be shared by diurnal fliers, as reported in honey bees and bumblebees as

they use optical flow cues during their flight.

(5)

Antennae help in directing motion, body orientation and detection of odour,

sound, temperature and humidity. All insects possess a pair of antennae that

help in flight stabilization and primarily act as sense organs and bear sensillae.

(6)

Thorax has three segments, pro, meso and metathorax. It is the main structure

for flight and locomotion (walking). Thorax is the main locomotor centre of

the body in insects as compared to other arthropods. Tergum plays a major

role in flight, by directing airflow.

(7)

A pair of the membranous wing is present on meso and metathorax later-

ally. These two segments are together known as pterothorax. Many insects

have two pairs of wings on pterothorax, which are held together by suitable

coupling devices during flight. The housefly has one pair of functional wings

on pterothorax which is common in Diptera.

(8)

Insects are hexapods, having jointed legs for walking, swimming and jumping

intotheair andapair of chitinous membranous wings for flight onpterothorax.

(9)

Each leg contains six jointed segments. Three pairs of legs are present on the

ventrolateral sides of the thorax. One pair of legs is present on each thoracic

segment.

(10)

The abdomen has no legs. The terminal part of the abdomen helps in excre-

tion, sensory and reproductive functions. The abdomen has relatively simpli-

fied segmentation. The abdomen normally has ten segments; however, their

number is variable in different orders and the last segments are modified as

genitalia.

(11)

Light- and sound-producing organs are also present in some insects such as

beetles, cicada and some plant bugs. Lampyridae (Coleoptera) is the best-

known luminescent group. Usually, the females are sedentary and attract the

males. The tymbals of Pentatomidae get buckled and produce sound. Cicadas

represent the highest development of sound production in insects. The ears

are also found in a great variety of insects.

Reaction involving light production is given below:

Mg++, Luciferase (Enzyme)

Luciferin + ATP ---------------------------------------> light production

Wings

(1)

Body covering and the wings are made up of chitinous exoskeleton which is

chemically a polymer of N-acetyl glucosamine. The integument gets hardened