There is a general tendency among robber-flies to reduce the bristles or hairs, especially the tergal bristles. Of course, many intermediary forms exist. A group that primitively kept those bristles, and afterwards had them reduced. This is also a good character for the establishment of evolutionary trends. Pilosity of antennal style .
Several genera show a more or less pilose antennal style.
A unique character is shown by a group of genera related to Ommatius , where the arista-like style shows a series of filaments on the underside. Wing venation . Most authors have relied on wing venation for the classification of Asilidae. The same as other characters, derived conditions appeared several times in several groups, and this character must be used with care. The primitively two-segmented palpus becomes reduced to a single segment.