xlviii INTRODUCTION. 



The Thorax. Brust. 



The upper portion of the body is divided into the 

 pronotnm, the mesonotum, and the metanotum. 



1. The pronotnm is often short, and usually appears 

 as a simple band with a posterior margin more or less 

 cut into an angular edge. It occasionally shows protu- 

 berances at the sides, and may occur reniform, trian- 

 gular, or trapezoidal. Sometimes it is wider than the 

 head and the eyes taken together, as in Idiocerus. 

 In some genera, like Centrotus, the pronotnm has long 

 spinous processes attached, which project over the 

 dorsum and reach beyond the tail. These adjuncts give 

 the insects uncouth and peculiar forms. In Ledra two 

 broad leaflets rise almost perpendicularly from the sides 

 of the pronotnm. The corresponding parts of the 

 under-side constitute the prosternum, and from it the 

 coxae of the first pair of legs take their spring. 



2. The mesonotum forms the larger part of the 

 thorax in the Tettigidag. It is channelled, and pro- 

 vided with large lateral bosses, from the sides of which 

 the tegmina or shoulder-scales spring, to cover the 

 insertions of the wings. On the under-side the meso- 

 sternum carries the second pair of legs, and the 

 opercula or lunate scales which cover the cavities 

 within which the singing organs of the stridulating 

 males are situated. 



3. The metanotum is but little seen above. It is 

 very narrow and deeply notched, to receive the meso- 

 notum. The elytra and wings spring from its borders. 

 The corresponding mesosternum gives off the third 

 pair of coxae with their legs. The scutellum is usually 

 large and triangular. 



I defer to another place a consideration of the 

 anatomy and function of the sounding apparatus, 

 which is very complex, and has engaged the attention 

 of various physiologists, both ancient and modern. 



