ORTHOPTERA. 



177 



being devoid of teeth, and the outer one long and slender. The fore-wings, or 

 elytra, do not differ from one another in structure, and, when at rest, are closely 

 applied to the somewhat thick and massive hind-body. The hind-wings are folded 

 many times, and may generally be seen projecting beyond the tips of the elytra. 

 The hind-legs are generally used in jumping, while the other two pairs are better 

 adapted for walking, although in the mole-crickets the fore-legs are thickened 

 and otherwise modified for use in burrowing. The tarsi of all the legs are com- 

 posed of either two or three joints. The abdomen bears near the tip two flexible, 

 velvety appendages, which are sometimes very long ; and in the females it usually 

 carries also a long exserted ovipositor. The chirping of crickets is produced by 

 rubbing the base of one elytron over the other; in which respect these insects 

 differ from most grasshoppers and locusts, and resemble only those grasshoppers 

 with long antennae, which belong to the family Locustidce. They resemble the 

 latter also in having their organs of hearing placed on the fore-legs. These organs 

 are lodged in the upper part of the tibiae, a little below their articulation with the 



1-4, field-cricket (Gryllus campestris) — (1) male, (2) female, (3 and 4) young and old larvae ; 5, MALE OF the 



house-cricket (Gryllus domesticus). 



femora, and consist externally of two small depressions or pits on opposite sides of 

 each tibia, with a thin membrane stretched across the bottom of each depression. 

 Inside the leg a tracheal vessel widens out between the two tympanic membranes, 

 to form a vesicular expansion, on which are distributed the end cells and rods of a 

 nerve which comes from the first thoracic ganglion. Crickets are found all over the 

 world, but only four species are British. Of these one {Nemobius sylvestris) may 

 be recognised by its small size, being little more than a third of an inch long. It 

 is usually found among the dead leaves in woods, and appears to be restricted in 

 its range to the southern counties. The field-cricket (Gryllus campestris), which 

 sometimes measures an inch in length, is generally of a black colour, and lives in 

 dry fields, where it is often heard though seldom seen on account of its retiring- 

 habits. The house-cricket (G. domesticus) has a reddish brown colour, and 

 is somewhat smaller than the field-cricket. It has well-developed wings, and 

 the female has a long ovipositor. The mole-crickets, of which there is one 

 British species (Gryllotalpa vulgaris), have such a peculiar structure that 

 they are easily distinguished from all other insects. They have a long, smooth, 

 shiny prothorax ; rather short, close-fitting elytra ; and under-wings which, when 

 vol. vi. — 12 



