 However, in birds, and some reptiles, males have two Z sex chromosomes and so are the homogametic sex, while females, with one Z and one W chromosome, are the heterogametic sex.Platypus males are heterogametic while females are homogametic.Among the insects, Lepidopterans (butterflies and moths) have heterogametic females, but in "Drosophila", males are the heterogametic sex.