Robber flies are voracious predators that hunt other flying insects. These flies are incredibly maneuverable and fast, allowing them to catch even the most agile prey. Robber flies typically perch on a high point, such as a blade of grass or a twig, and wait for a potential victim to pass by. When they spot an insect, they dart out, snatching it from the air with their powerful front legs.

The front legs of robber flies are uniquely adapted for hunting. They are long and strong, with a row of sharp spines along the inner edge of each leg. These spines allow the robber fly to hold its prey securely while it uses its mouthparts to deliver a fatal bite.

Robber flies are not particularly picky eaters, but they do have a preference for certain types of insects. Flies, bees, wasps, and dragonflies are all common prey items for robber flies. Robber flies will also occasionally eat other robber flies, making them one of the few insects known to practice cannibalism.

While robber flies are not considered to be harmful to humans, they can be a nuisance. These flies are often attracted to bright lights, and they can sometimes get inside homes and businesses. Robber flies can also bite humans if they are provoked, but these bites are usually not serious.