Robber flies, also called assassin flies, are cosmopolitans with several thousand described species. They can be found in grasslands throughout the world.
Robber flies are between 3 and 50 millimeters long and are not regarded as cute. They are covered with short, rough hairs. Between the fly’s two compound eyes there is a depression and 3 small, simple eyes [ocelli]. The fly’s abdomen is elongated and its legs with bristles are notably lengthy. The hair of some species is gray and yellow, making them appear like bees or wasps.
The robber fly is known for its hunting and feeding tactics: It catches other flying insects in mid-air, stabs a tube into the victim and injects paralyzing, toxic saliva. The saliva liquefies the internal organs of the prey which are then sucked up. The robber fly will prey on most flying insects, though it seems to prefer bees and wasps. If a robber fly bites a human, the bite can be painful.