THE CLASSIFICATION OF INSECTS 65 



long, thread-like antennae and four-jointed tarsi. An 

 " ear " is often present at the base of each front tibia, 

 or shin ; while the males of many species " chirp " by 

 rubbing a file-like ridge, situated on the underside of one 

 wing, over a sharp ridge on the upper surface of the wing 

 beneath. In a few genera both sexes are provided with 

 sound-producing structures. Tree grasshoppers feed upon 

 leaves, but many species also attack caterpillars and other 

 insects. The family is most numerously represented in 

 the tropics, but several species — notably the large green 

 grasshopper (Locust a viridissima) — are found in Britain. 



The crickets (Gryllidce) resemble the tree grasshoppers 

 in many respects, their " ears " and chirping organs being 

 similarly placed ; but they have not more than three tarsal 

 segments. They are represented in all parts of the world, 

 four species being found in Britain. Of these, the wood 

 cricket (Nemobius sylvestris) is apparently confined to the 

 neighbourhood of the New Forest ; while the field cricket 

 {Gryttus campestris) and the mole cricket (Gryllotalpa 

 vulgaris) occur only in a few isolated localities. But the 

 house cricket (Gryllus domesticus) is probably the most 

 familiar of all domestic insects. Its ancestral home is said 

 to be North Africa — hence, probably, its well-known pre- 

 ference for the hearth and the oven. Most crickets live in 

 subterranean burrows, while the majority are vegetable 

 feeders, though the mole cricket is largely carnivorous. 



Order IV. — Plecoptera. 



This order includes the single family of the stone- 

 flies (Perlidce) which was formerly grouped with the 

 Neuroptera. The mouth-parts are formed for biting, 

 while the wings of both pairs are similar in texture, with 

 a complicated net-veining. In the male, however, the 



