Asilidae (“robber flies” or “assassin flies”) is the 3rd most speciose family taxon of Diptera with more than 7,500 described species. Robber flies occur world-wide and they have conquered major islands and even many smaller island groups, but are not found in the Hawaiian Islands, for example, on which other insect taxa diversified successfully. Robber flies are exclusively predatory flies both in the larval and adult stage, which is only found in a few clades within Diptera. The predatory lifestyle particularly of the adult with numerous autapomorphic features in the proboscis and internal head structures can be postulated to have been the major driving force in the successful species diversification of this taxon. Robber flies are actively collected by both specialized dipterists and general entomologists around the world and chasing these often large, brightly colored visual predators is fun and rewarding.