1889] 



THE YOUNG NATURALIST. 141 



which there is not a vestige of the front pair, nor are they degenerated 

 by any mesothoracic attachment (Westwood.) 



The production of sound by insects has ever been a fruitful theme 

 for controversy and speculation, and we must not expect to find it 

 evolved by any of those methods with which we are familiar. We 

 are accustomed to associate sound — voice, I may say — caused by liv- 

 ing creatures with the passage of a current of air over certain flexible 

 cords during breathing ; but among the insects we must be prepared 

 to find very different modes of producing sounds, not unfrequently 

 of high musical pretensions. The Orthoptera are notorious musicians, 

 but the province of the present paper confines me to one group, viz., 

 the Achetidce, or crickets. The house and the field cricket, respectively 

 Acheta domestica and Gryllus camfiestris, are known in particular for the 

 sound they produce, a kind of clear chirrup, which can be heard a 

 considerable distance. Only the males of both species possess vocal 

 organs, which they use with much force and vigour, chirruping not 

 only by day but also by night. 



I have given, at Fig. 15, a detailed drawing of the left wing-cover 

 or tegminus of the male House Cricket, the unique pattern of the 

 neuration at once leading us to suppose that some very important 

 office is fulfilled by this important organ. The right and left wing 

 covers resemble each other in all points but one, to which I shall 



presently have occasion to minutely refer. 

 We first notice that the tegmina consist 

 of two portions, divided by a parallel series 

 of four nervures, the lesser (or third part) 

 being deflexed, and covering the sides of the 

 abdomen, the remainder constituting a dor- 

 sal protection, and lying flat. It is on this 

 latter portion that the stridulatory organ is 

 placed, occupying the greater part of a basal 

 nerve that is bent to almost a right angle. 

 The peculiar structure of this nervure, how- 

 ever, only becomes apparent under a higher 

 magnification, and is shown at Fig. 16. It 

 will be seen that this branch is bridged over 

 by a number of parallel, elevated ridges, not 

 bending round the curve of the nervure, 

 but so raised, or built up against it, as to 

 form, en masse, by their exposed edges, one horizontal plane. This 

 serration, if I may so term it, is peculiar in the case of the left wing- 



