Composition

Insects belong to phylum Arthropoda. They share similarities in the segmented body consisting of 20 segments which are incorporated into three tagmata, a head, thorax and abdomen. There are three pairs of segmented thoracic legs; unsegmented legs can be at larvae of some insects.

Insects are the largest group of organisms numbering about one million of species Entomologists early divided insects into two groups, Apterygota (wingless) and Pterygota (winged insects) having two pairs of wings. In modern classification Insecta is divided into entognathous insects (Entognatha) with mouthparts sunken into a depression of head and ectognathous insects (Ectognatha) with open mouthparts. Entognatha contains orders Collembola (springtails), Protura, Diplura. Ectognatha consists of 34 orders including wingless silverfishes. 85 % from number of insects fall at four orders. These are Coleoptera (beetles), Hymenoptera (sawflies, bees, wasps, and ants), Lepidoptera (moths, butterflies), Diptera (mosquitoes, gnats, flies).