The family Asilidae contains what are commonly called Robber Flies. There are a large number of species in this family and identification can be difficult, to which I can certainly attest.

Here are some of the characteristics which differentiate the family Asilidae:

• fast flying predators
• a facial beard of bristles
• most (but not all) species have tapering abdomens

The genera of Asilidae for which I have photographs are listed below.

• Proctacanthus

• Hull, Frank M.. Robber Flies of the World: the Genera of the Family Asilidae. Washington: U.S. Government Printing Office, 1962.
  
• Milne, Lorus J., and Margery Milne. National Audubon Society Field Guide to North American Insects and Spiders. New York: Alfred A. Knopf, 1980.