Bugs of the family Belostomatidae are fierce predators which stalk, capture and feed on aquatic crustaceans, fish and amphibians. They often lie motionless at the bottom of a body of water, attached to various objects, where they wait for prey to come near. They then strike, injecting a powerful digestive saliva with their mandible, and sucking out the liquefied remains. Their bite is considered one of the most painful that can be inflicted by any insect (the Schmidt Sting Pain Index excludes insects other than Hymenoptera); the longer the bug is allowed to inject its saliva, the worse the resulting bite, and as the saliva liquefies muscle tissue, it can in rare instances do permanent damage. Adults cannot breathe under water, and must surface periodically for air.[1] Occasionally when encountered by a larger predator, such as a human, they have been known to "play dead" and emit a fluid from their anus.[1] Due to this they are assumed dead by humans only to later "come alive" with painful results.[1]