Arthropods are the largest group of animals (80% of all animal spp.) occurring in the water, soil, air, etc. The main characteristics of arthropods are hard chitinous exoskeletons, segmented body, and jointed legs. The word Arthropoda has been derived from two Greek words: arthros meaning “joint” and podos meaning “foot.” The outer covering of arthropods is called exoskeleton formed by chitin. The exoskeleton is composed of different chitinous plates which are called sclerites. The dorsal sclerite is called tergum; ventral sclerite, sternum; and lateral sclerite, pleuron. The old cuticle is cast off periodically and a new cuticle is formed. This biological phenomena of arthropod is called ecdysis. The body of arthropod is metamerically segmented.