Robber flies (Order Diptera, Family Asilidae) are extremely successful predators and have voratious appetites. They mostly prey on other insects and are capable of attacking and immobilising bees, wasps, dragonflies, grasshoppers and even spiders, however, they tend to be opportunistic feeders, feeding on whatever insects happen to be available in a particular habitat.
When on the hunt, robber flies establish a perching location, usually in a sunny open area, in order to locate suitable prey. Once located, robber flies catch their prey in mid air, using their strong legs to grasp and their modified mouthparts, in the form of a stabbing proboscis, to inject them with saliva containing neurotoxic and proteolytic enzymes. The neurotoxins paralyse the prey and the proteolytic enzymes digest proteins in the body tissues. The robber fly will then return to its perch and consume the liquidised body tissues of the prey.
Photos courtesy of Keith Power, Toowoomba, Qld.