Mouth parts adapted for sucking; body naked or with bristles and spines; prothorax well developed; body compressed; tarsi with five segments; wings absent. Metamorphosis complete. The larva is a wormlike creature. Fleas. COLEOPTERA Adult with four wings (rarely wanting), the first pair horny or leathery, veinless, forming wing covers which meet in a line along the middle of the back. Mouth parts of both immature stages and adults adapted for biting and chewing. Metamorphosis complete. The larvæ of many species are known as grubs. Beetles. HYMENOPTERA Adult insect with four, usually transparent, wings, wanting in some species. Mouth parts adapted for biting and sucking; palpi small; tarsi four or five-segmented. Metamorphosis complete. Parasitic four-winged flies, ants, bees, and wasps. SIPHUNCULATA AND HEMIPTERA a. Legs with claws fitted for clinging to hairs; wings wanting; spiracles of the abdomen on the dorsal surface. (= ANOPLURA = PARASITICA) SIPHUNCULATA. b. Legs not modified into clinging hooks; tibia and tarsus very long and slender; tibia without thumb-like process; antennæ five-segmented HÆMATOMYZIDÆ Endr. _Hæmatomyzus elephantis_ on the elephant. bb. Legs modified into clinging hooks; tibia and tarsus usually short and stout; tibia with a thumb-like process; head not anteriorly prolonged, tube-like. c. Body depressed; a pair of stigmata on the mesothorax, and abdominal segments three to eight; antennæ three to five-segmented. d. Eyes large, projecting, distinctly pigmented; pharynx short and broad; fulturæ (inner skeleton of head) very strong and broad, with broad arms; proboscis short, scarcely attaining the thorax. PEDICULIDÆ e. Antennæ three-segmented. A few species occurring upon old world monkeys. _Pedicinis_ Gerv. ee. Antennæ five-segmented. f. All legs stout; thumb-like process of the tibia very long and slender, beset with strong spines, fore legs stouter than the others; abdomen elongate, segments without lateral processes; the divided telson with a conical process posteriorly upon the ventral side. PEDICULUS L. g. Upon man. h. Each abdominal segment dorsally with from one to three more or less regular transverse rows of small setæ; antenna about as long as the width of the head. Head louse (fig. 65). P. HUMANUS. hh. "No transverse rows of abdominal setæ; antenna longer than the width of the head; species larger." Piaget. Body louse of man. P. CORPORIS. gg. Upon apes and other mammals. _P. pusitatus_ (?).