Commonly all insects are called “bugs”; however, the term “bug” actually refers to a specific order of insects, the Hemiptera, or so-called “true bugs.” Not all members of the group are aquatic, however there are nearly 5,000 aquatic or semiaquatic species worldwide. They are hemimetabolous, meaning that the life cycle does not have a pupal stage, and adults and larvae look very similar, except for the lack of wings when immature (wing pads may be present). True bugs can almost always be distinguished from other insects by the presence of a pointed beak or rostrum; this is a set of piercing-sucking mouthparts, usually long, that is held beneath the body (ventrally) when not feeding. These insects are often herbivores, feeding on plant fluids, or predators that inject their prey with digestive enzymes which liquefy the tissues so that they can be easily sucked back up through the straw-like mouth.