Robber flies (family Asilidae) are among the most impressive predatory insects in Arizona, with over 1,000 species occurring in North America and many found in the Sonoran Desert. They are robust, bristly flies with a distinctive beard of facial bristles, powerful legs for grasping prey, and a strong, piercing proboscis. Robber flies are aerial ambush predators that catch other insects — including bees, wasps, dragonflies, grasshoppers, and beetles — in mid-flight, injecting them with saliva that contains neurotoxic and proteolytic compounds to immobilize and liquefy their prey. They are entirely beneficial from a pest control perspective, preying on many pest species. Robber flies are not household pests and do not infest structures. However, they can deliver a painful defensive bite if handled, and some species mimic bumblebees convincingly enough to cause alarm.