The primary goal of this research is to understand the evolutionary mechanisms involved in causing morphological and behavioral differences in the sexes. This is a particularly active and controversial area in evolutionary biology. Several competing alternative explanations are still being considered, in part because appropriate data have not yet been obtained. While any group of species that showed differences between members of the opposite sexes could, in principle, be used, this research focusses on a group of flies which have three important attributes that make them ideal for this research. In some species, males have eyes on the ends of stalks which can attain lengths greater than two.times the male's body length while females have much shorter stalks. Other closely related species show less dramatic sexual dimorphism and a few species exhibit no dimorphism at all and have very short eye stalks. The group is uniquely suited to this research because 1) these dramatic differences are limited to a single trait. 2) several species occur in the same local area and can be studied in the field, and most importantly, 3) most of these species can be reared in the laboratory. This latter feature is critical because breeding experiments can identify the genetic basis underlying this trait as well as the genetic influence on female mate choice behavior. The results of this research should not only allow better understanding of the exaggerated head form of these flies, but should also provide insight into the mechanisms and consequences of sexual dimorphism in other species.//
