Of an estimated 5-10 million species of insects, probably not more than a fraction of 1 per cent interact, directly or indirectly, with humans. Insects have been associated with man's interests in many ways. Their ability to both benefit and harm mankind makes this relationship a unique one. They play a silent role in maintaining the balance of nature; some [...]
The classification of insects into various orders is based on the presence or absence of wings and their venation, type of mouth parts, type of metamorphosis and characteristics of antennae and tarsi. The class Insecta has two subclasses, Apterygota, the primitive wingless insects, and Pterygota, insects with wings (although some of them may be secondarily apterous). Initially, there were 29 [...]
The eggs in insects have less food materials than those in birds and reptiles. Therefore, unlike birds, the young ones of insects emerge at an early stage of development and are much smaller than, and quite different in body shape, from the adults. Moreover, the young have a covering of inflexible exoskeleton which they have to shed a number of [...]