258 Introduction to the Synopsis of the Acrididce. 



The thorax is the middle portion of the body, to which arc attached 

 1 he ?ix legs, and also the four wings, when present. In order to ac- 

 commodate the strong muscles necessary to the motion of these mem- 

 bers, it is the most robust of the three parts of the body. It consists 

 of three parts, each composed of several pieces ; the front portion, 

 which bears the first pair of legs, is the prothorax; the middle portion, 

 which bears the middle pair of legs and the upper wings (elytra) is the 

 vu'sothorax ; the posterior portion, which bears the third pair of legs 

 and the under wings (iving^ proper), and to which the abdomen is 

 joined, is the metathorax. 



The different surfoces of these divisions are distinguished by sepa- 

 rate names ; thus the dorsal portion of the protothorax is the prono- 

 tum, and the ventral portion the prostermim; the dorsal portion of 

 the mesothorax is the mesonotum, and is usually covered by the pro- 

 notum ; the ventral portion is the Hfesosfer/mm; the dorsal portion of 

 Tl\e metathorax is the meianotum; the ventral surfiice the metasteriium . 

 The whole of the under surface of the thorax taken together is tht- 



df'.rnum. 



The most important of these divisions, in describuig genera a)id 

 species, is the pmnotum ; this is the shield which covers the front part 

 of the body immediately behind the head, reaching down the sides, 

 nearly or quite to the insertion of the front legs ; it usually extends 

 back on the doi'sum of the thorax, so as to cover the base of the 

 elytra ; but in the subfamily Tetttgino} it extends back over the abdo- 

 men to its extremity. Its surface is considered with reference to three 

 planes — the upper surfjxce (dorsum) and the two sides ; but there are 

 wide variations from this typical form. When these areas are clearly 

 distinguishable there is a raised line, sharp angle, or obtuse ridge run- 

 iiino- alonir each margin of the dorsum, where it connects with the 

 side ; these are called the lateral carina;. In most species of the family 

 there is a raised line or keel along the middle of the pronotum, called 

 the median carina ; this is sometimes but an indistinct line, in other 

 species it is quite distinct ; in some slightly elevated, when it is said to 

 be sub-cridate ; and sometimes it is quite elevated, when it is called 

 cristate. Tiie term carina is sometimes, though with doubtful pro- 

 priety, applied to the obtusely-rounded angle formed by the deflection 

 of the sides of the pronotum from the dorsum (as in Caloptenus, and 

 even in Pezotettix, where the pronotum is almost cylindrical). I have, 

 therefore, in some cases, introduced the term humerus or humeral angle. 

 to represent this part when it can not properly be called a carina. In 

 some cases the sides slope upward to the median carina, leaving no 

 lateral cariila or angle (as in Tropidolophus and Tropidacris) ; in other 



