Robber Flies

Description

Robber Flies, also sometimes called assassin flies, are as violent as their names imply. They are large, opportunistic predators which kill and eat just about any other insect they can. They have a short proboscis but use it to impale and liquefy their prey similar to assassin bugs (reduviidae). Robber flies come in many forms but are typically quite hairy with stout legs and long abdomen. Like some other families of diptera (the true flies), some species of asilidae imitate the shape and coloration of hymenoptera, usually eusocial (non-solitary) bees. However an astute viewer will not be fooled because hymenoptera have two pairs of wings while diptera have two. Many supposed bees the viewer has seen, if they are not an immediately familiar form such as the ubiquitous western honeybee, are likely in fact true flies - perhaps even these incredible predators!

Species

Unknown Asilidae in Texas

"Robber Flies"

Images of Robber Flies

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An injured robber fly resting on the sidewalk in late summer. Although I believe it was alive, it did not respond to any motion or light touch.
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The fly is clearly missing most of its left first leg, perhaps a recent injury. The charateristic "dip" between its enormous eyes and of course its single pair of wings are hallmarks of a true fly.
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A different robber fly is here found dead, grasping its prey, a paper wasp. I've lifted them on a twig for a better view but the lighting was poor.
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Placed back on the ground, the robber fly and its prey can be clearly seen. Although on a bike path they do not appear crushed so it is unclear what killed them.