True bugs belong to the order Hemiptera and undergo an incomplete metamorphosis involving three stages: egg, nymph and adult. Nymphs molt several times before becoming adults. Bugs are often confused with beetles, which belong to the order Coleoptera and undergo a complete four-stage metamorphosis of egg, larva, pupa and adult.
True bugs are part of the same order as grasshoppers, cicadas and aphids. The name Hemiptera refers to the structure of the upper wings, which typically have a leathery basal part. The rest of the wing is membranous. When the wings are at rest, they lie flat over the body with crossed wingtips. The triangular portion of the thorax that lies exposed between the wings, the scutellum, is usually prominent. Bugs have mouth parts adapted for piercing or sucking.
There are about 82,000 identified species of true bugs, compared to some 390,000 species of beetles. Bugs are found all over the world in a wide variety of habitats and are the only insect group with oceanic species. Bugs include a number of pests, such as bed bugs, stink bugs and squash bugs, but other types, such as assassin bugs, feed on other insects and benefit people by providing pest control.