DIPTERA ([page 285])
The adult insect is provided with two, usually transparent, wings, the second pair of wings of other insects being replaced by a pair of halteres or balancers. In a few rare species the wings, or halteres, or both, are wanting. The mouth parts, which are not segmented, are adapted for sucking. The tarsi are five-segmented. Metamorphosis complete. The larvæ, which are never provided with jointed legs, are variously known as maggots, or grubs, or wrigglers. Flies, midges, mosquitoes.
SIPHONAPTERA ([page 316])
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.