TRUE ORTHOPTERA 3141 



The book lice and the other insects classed with them in the family 

 Psocidce form another small group of Pseudoneuroptera. They are 

 mostly very small insects, with a proportionately big head, swollen in front, and 

 carrying prominent eyes, three ocelli, and bristle-like antennae. Their mandibles 

 are horny at the tip, but the other parts of the mouth are usually soft and mem- 

 branous; the maxillae being bilobed, with four- jointed palpi, and the palps of the 

 bifid labium rudimentary. The middle segment of the thorax is the largest, and 

 the prothorax is usually very short and narrow. The wings, which are wanting in 

 some species, are slanting in repose, like the sides of a roof, and cover over the 

 abdomen; they are of an almost glassy transparency, and have, as a rule, an open 

 system of neuration. The tarsi are composed of two or three joints. Most species 

 of Psocidce live in the open air, and feed on fungi, lichens, and the fragments of 

 other plants; the largest European species (Psocus lineatus] being scarcely more 

 than a quarter of an inch long. 



The Mallophaga, commonly known as bird lice, are small wingless 

 insects, resembling ordinary lice to some extent, but differing from them 

 in many characters, and especially in the structure of the mouth, which is fitted 

 for taking food by biting instead of sucking. They form a distinct group, now 

 generally placed in the Pseudoneuroptera, though 

 some entomologists assign it a position near the 

 Pediculina or true lice. The bird lice are flat- 

 bodied insects, with a broad head, varying a good 

 deal in form, and a thorax which usually appears 

 to consist of only two segments. Their antennae 

 are short and composed of three, four, or five 

 joints; and their eyes, when present, are simple. 

 The mandibles appear as short hooks, sometimes 



toothed on the inner side; the maxillae are ^G^PS OC US lineatus (enlarged three times), 

 and said to be always palpless; while the lower 



lip is distinct and often bears palpi. The legs are short and stout, and have 

 two-jointed tarsi, each of which carries at the end either one or two claws. As 

 bird lice are found on mammals as well as on birds, their name is to some 

 extent misleading. 



TRUE ORTHOPTERA (Orthoptera Genuina) 



The insects of this suborder differ chiefly from those of the last group in the 

 characteristics of their wings, in which the two pairs are not formed alike. The 

 fore-wings, which are usually stiff and tough, and in some cases horny, serve as 

 wing covers, and are generally spoken of as elytra; whereas, the hind-pair are mem- 

 branous, and capable of being folded longitudinally, or both longitudinally and 

 transversely. The division of the ligula, or terminal piece, of the lower lip into 

 two or four lobes, is usually more complete than in the Pseudoneuroptera. It is 

 usual to divide the true Orthoptera into two series or tribes the Saltatoria, with 



