According to Andrew Williams:"Robber flies are strong, hairy, active, predatory flies. They're a common insect and can be spotted flying in a darting motion while preying on a wide variety of insects. As a rule, they're fairly slender, strong for their size, and equipped with a large, tapering, hard beak, which contains a sharp lancet. This weapon is thrust out creating a severe wound in the bodies of captured prey insects. A robber fly's beak tip is covered with stiff bristles, designed to secure it within the wound it creates." 22-2-2011