The genus Lasiopogon is a widespread group of robber flies (Diptera: Asilidae) inhabiting the north temperate parts of the Earth. This study is the first to examine the genus as a complete entity and clearly define intrageneric relationships. It is also the first to pay special attention to the male and female genitalia, important structures in the taxonomy of the genus. There are 118 known species of Lasiopogon, about half of these yet to be described. Dr. Cannings gives a cladistic overview of some defined species groups, and provides a detailed taxonomic and phylogenetic analysis of the 7 species groups and 29 species in the opaculus section, comprising about 25 per cent of the genus. He describes 14 new species in this section and redescribes the others. Dr. Cannings also offers a biogeographic hypothesis of the history of Lasiopogon, suggesting that the genus may have originated in Laurasia as early as the late Jurassic period.