Robber flies inhabit all regions of the world except the arctic regions. The highest diversity is in the subtropical and tropical regions, but our knowledge of these fauna is insufficient and the number of new described species increases rapidly. It seems to be that robber flies prefer open areas. In some deserts they are amongst the dominant predators. Our impression of the distribution is dependent on the knowledge of species. A first assumption is possible on the subfamily level. For example: The Leptogastrinae are distributed world-wide, whereas the Ommatiinae are concentrated in the Oriental, Afrotropical and Australian regions - the Stichopogoninae in the Palaearctic region - and the Apocleinae in the Neotropics.

The diversity is quite higher in Southern Europe, around the Mediterranean. North of the Alps, the number of species is reduced by different cold phases of the Pleistocene and the climate.
The knowledge of the northern fauna is high in comparison with that of the southern fauna. In the North some taxa are still uncertain and the presence of undescribed species is probable. In contrast to that, many problems are waiting in the South and few revisions are made. One of the most significant papers is that of THEODOR (1980), who revised the fauna of Israel. His thorough and comprehensive work set a new standard in describing new taxa.
The knowledge of the distribution depends on the number of workers. The highest rate of new described taxa is found in Southern Africa, Eastern Russia and Chile during the last 30 years. The results make it clear that the research on Asilidae has just started. Therefore we need more enthusiasts for this interesting family.