This study is based on a similar study made by Claudeous J. D. Brown in 1928, and published in 1929. The species he used have been rechecked, and additional ones have been studied. The species considered in this study represent three of the four subfamilies of North American Asilidae. These three subfamilies are Dasypogoninae, Laphriinae, and Asilinae. This study is limited to those species in the Brigham Young University Collections, and to species recorded in print. No claim is here made that all the forms inhabiting the state have been discovered, in fact the writer is well aware of the pro bability of many undiscovered species.