Choose the character unrelated to Drosophila.

In the fruit fly Drosophila melanogaster, morphological sex differentiation is evident in various aspects, primarily through differences in external physical characteristics. Drosophila exhibits sexual dimorphism, which means that males and females have distinct physical features. 

The most prominent morphological difference is in the genitalia. Males have specialized structures called claspers at the end of their abdomen, which are used for copulation. Females have a single genital opening, which is distinct from the male's genitalia.