Robber flies look like they belong in a sci-fi movie! They have bulging eyes, skinny legs, and a terrifyingly long proboscis (feeding tube) with a needle-like appendage on end. Robber flies are ambush predators, meaning they lie in wait before attacking their unsuspecting prey. When a robber fly finds a victim, it quickly lands on its back and inserts its proboscis into a vulnerable spot, such as the eye or the body cavity.