Most species of assassin bugs are considered beneficial because they help control insect pests. As with most true bugs, it has thickened forewings with membranous tips for handling prey. When at rest, the extended, segmented beak can be folded back underneath its body. Its folded wings overlap, giving the back a characteristic shape. Adults are commonly black, reddish, or brown, with long, slender legs, a narrow head, and round, beady eyes.
Some species have sharp barbs on their forelegs to prevent prey from escaping.
All assassin bug species are predatory, primarily feeding on caterpillars and other insects. The assassin bug uses its needlelike beak to impale prey. It then injects a venom that both paralyzes and partially digests the prey. The body contents of the victim liquefy and are sucked out with the assassin bug's strawlike mouth parts. A few species, like the western bloodsucking conenose, commonly bite humans and other mammals.