Piercing mandibles, retracted within the head-capsule. First maxillae also modified as piercers; maxillae of both pairs with distinct palps. Both pairs of wings similar, narrow and fringed. Four Malpighian tubes. Cerci absent. Ovipositor usually present. Young resembling parents, but penultimate instar passive and enclosed in a filmy pellicle. Includes three families of Thrips (see THYSANOPTERA). Order: _Hemiptera_. Mandibles and first maxillae modified as piercers; second maxillae fused to form a jointed, grooved rostrum. Wings usually present. Four Malpighian tubes. Cerci absent. Ovipositor developed. Includes two sub-orders:-- 1. _Heteroptera_: Rostrum not in contact with haunches of fore-legs. Fore-wings partly coriaceous. Young resembling adults. Includes the bugs, terrestrial and aquatic. 2. _Homoptera_: Rostrum in contact with haunches of fore-legs. Fore-wings uniform in texture. Young often larvae. Penultimate instar passive in some cases. Includes the cicads, aphides and scale-insects (see HEMIPTERA). Order: _Anoplura_. Piercing jaws modified and reduced, a tubular, protrusible sucking-trunk being developed; mouth with hooks. Wingless, parasitic forms. Cerci absent. Four Malpighian tubes. Young resembling adults. Includes the family of the Lice (_Pediculidae_), often reckoned as Hemiptera (q.v.). See also LOUSE. Sub-class: ENDOPTERYGOTA. Hexapoda mostly with wings; the wingless forms clearly degraded or modified. Maxillulae vestigial or absent. No locomotor abdominal appendages (except in certain larvae). Young animals always unlike parents, the wing-rudiments developing beneath the larval cuticle and only appearing in a penultimate pupal instar, which takes no food and is usually passive. Order: _Neuroptera_. Biting mandibles; second maxillae completely fused. Prothorax large and free. Membranous, net-veined wings, those of the two pairs closely alike. Six or eight Malpighian tubes. Cerci absent. Larva campodeiform, usually feeding by suction (exceptionally hypermetamorphic with subsequent eruciform instars). Pupa free. Includes the alder-flies, ant-lions and lacewing-flies. See NEUROPTERA. Order: _Coleoptera_. Biting mandibles; second maxillae very intimately fused. Prothorax large and free. Fore-wings modified into firm elytra, beneath which the membranous hind-wings (when present) can be folded. Cerci absent. Four or six Malpighian tubes. Larva campodeiform or eruciform. Pupa free. Includes the beetles and the parasitic _Stylopidae_, often regarded as a distinct order (_Strepsiptera_). (See COLEOPTERA.) Order: _Mecaptera_. Biting mandibles; first maxillae elongate; second maxillae completely fused. Prothorax small. Two pairs of similar, membranous wings, with predominantly longitudinal neuration. Six Malpighian tubes. Larva eruciform. Pupa free. Cerci present.