Robber Fly

Family Asilidae — the robber flies, also called assassin flies — contains about 7,500 species worldwide and is one of the most species-rich groups of predatory insects. All species are aerial ambush predators of other flying insects. The hunting strategy is highly stereotyped: the robber fly perches on a vegetation tip with the head facing the sun (so prey is silhouetted), scans the field of view with large compound eyes, launches with explosive 0.05-second lunges to intercept passing prey in midair, and returns to the perch with the captured insect impaled on the curved hypopharynx. The fly then injects neurotoxic and proteolytic saliva (paralyzing the prey instantly and beginning external digestion), and drinks the liquefied internal tissues over the next 5-30 minutes. Robber flies are remarkable for the size and toughness of their prey: documented prey items include honey bees, bumblebees, vespid wasps, dragonflies, damselflies, butterflies, and a famous 1979 record of a Hyperechia robber fly taking down a sunbird in Africa. Promachus hinei is the largest robber fly in eastern North America (about 4 cm body length). Some Asilidae species (notably the Microstylum and Hyperechia genera) are extreme bee-mimics — coloration, pile, and flight pattern all match the bees they prey on, allowing them to hunt within bee swarms.