The word arthropod comes from the Greek which means “jointed leg”. They are with jointed limbs and segmented bodies. Arthropods are including among invertebrates. Their exoskeleton is made up of chitin which is a polymer of glucosamine. Beetle, mites and some crustaceans are having bio mineralized cuticle which has calcium carbonate. Epicuticle, exocuticle and endocuticle are three major layers of cuticle. These three layers are collectively called procuticle. Their growth is restricted because exoskeleton cannot stretch therefore they shed their old exoskeleton by the process of moulting. They are having wide variety of respiratory systems. Their bodies are internally segmented. Several thousand independent ommatidia are present in their compound eyes.