Q. How are the excretory systems of the three major arthropod classes constituted?

In crustaceans a pair of excretory organs called green glands exists, the green glands collect residuals from the other parts of the body and blood. They are connected by channel to excretory pores located under the base of the antennae and these pores release the excretions outside.

In insects small structures known malpighian tubules gather wastes from the blood and throw them into excretory channel that open in the intestine, in these animals excretions are eliminated together with feces.

In arachnids, as well malpighian tubules, there are coxal glands located in the cephalothorax near the limbs that also participate in excretion.