INSECT VAKIETY, 183 



In Locustina, Grijll'ul(e, and Phasmidce (/) stridulation results 

 from mutual friction of the elytra, which generally assume 

 masculine differential development in their membranes^ with 

 tumerosity and induration of certain veins. Among the crickets 

 it is the male alone that sings ; and their elytra folded, as in Fig. m, 

 page 151, have the whole membrane more or less tense and 

 glassy to act in the capacity of sounding-boards, and impress 

 the vibrations caused by the file on the included air. The file 

 does not vary much in regard to position; if we examine with 

 a lens the wing-covers of the House Cricket {Gri/llm domesficas), 

 or of the Field Cricket {G. campestris) , or of the Mole Cricket 

 {Gryllotaljpa vuhjaris), we shall find it well developed (Plate VI., 

 Fig. 10) beneath either wing-cover, on the vein separating the 

 intei-mediate field from the anal, which is strong, horny, or chiti- 

 neous, sunk in the membrane above, and prominent at the 

 under side, in the form of an italic y, and somewhat parabolic 

 (Plate II., Fig. 8, 1). Now, as this vein constitutes a much more 

 elongate file than is found in the Locustina, its teeth are conse- 

 quently more numerous ; Dr. Landois estimates the number in 

 the field-cricket from one hundred and thirty-one to one hundred 

 and thirty-eight ; in the house-cricket he finds about one hundred 

 and thirteen, and in the mole-cricket eighty to eighty-two. Their 

 shape also is different; for in the leaf -crickets they are formed 

 like fiddle-bridges, and here they are solid triangles. (Compare 

 Fig. 4c with Figs. 4a, 4b.) This vein, then, being the bow, 

 shrill- vein, or file, where is the clasp over which it sounds ? If 

 we next examine the part above, where the file of either elytron 

 scrapes when the wing-covers are rubbed together, we shall not 

 fail to find this in a branch the notched vein gives off towards 

 the base of the wing-cover, which is smooth and prominent, and 

 along which the file works a little obliquely (Fig. 8, s) . 



" The field-cricket," says Colonel Goureau, "is common 

 in the province of Gex, where the warm and sandy soil is very 

 favourable to its increase. The larva is produced from an e^o^ of 

 a dirty-whitish colour at the end of July, and these inhabit a 

 little hole scooped in the soil. At the entrance of this they con- 

 ceal themselves. At this period of their lives they are some- 

 times met with in the evening during twilight, collected together 

 in great numbers, and crossing roads and footways, leaping like 



