Sexual dimorphism is the difference in the form of individuals of different sexes but of same species. Sexes in Ascaris are separate and sexual dimorphism is well defined. Males are smaller than females. They possess a recurved tail with pre and post anal papillae, a cloaca, and a pair of spicules or penial setae. In Anopheles, the ends of maxillary palps in males are club-shaped while in females they are not.