INTRODUCTION. XV 



ing the sides of the under surface ; and a middle piece, the pre- 

 sternum, between and in front of the anterior legs. The side 

 pieces are best seen in the Carabidse ; the anterior pair is called 

 the episterna, and the hind pair the epimera. Most frequently 

 the sutures between these pieces, and between them and the pro- 

 notum are entirely effaced, so that the dorsal surface and the 

 flanks form a continuous piece ; the sutures between the prester- 

 num and the flanks are always distinct, and are called prosternal 

 sutures. The cavities in which are inserted the anterior legs are 

 called anterior coxal cavities, and are either entire when they 

 are inclosed behind by the junction of the prosternum and the 

 epimera, or open, when a space is left protected only by mem- 

 brane ; they are separate when the prosternum extends between 

 them, or confluent when the prosternum is not visible between 

 them. 



For strengthening the anterior opening of the prothorax which 

 receives the head, one pair of horny plates is included in the 

 membrane ; they are called antecoxal plates, and are usually 

 invisible without breaking the insect ; I have found them very 

 largely developed in the genus Chauliognathus of the sub-family 

 Telephoridae. 



The second segment is called the mesothorax, and in Coleoptera 

 is very closely united with the third segment or the melathorax, 

 which is also closely connected with the abdomen ; these parts 

 together form the trunk, or main body of the insect. 



These two segments support on the inferior surface the middle 

 and hind legs, and at the sides of the dorsal surface the icings. 



The dorsal surfaces of these two thoracic segments are covered 

 by the elytra, consequently invisible without dissection ; they are 

 called mesonotum and metanotum, and consist each of four pieces, 

 separated by sutures, and named, commencing with the anterior 

 one of each segment, proscutum, scutum, scutellum, and post- 

 scutellum. No use is made of them in classification, except that 

 the small triangular piece, usually visible between the elytra at 

 their base, is sometimes mentioned under the name scutellum. 



The under surfaces consist of the same pieces as the prothorax, 

 viz : respectively, mesosternum, with its epimera and episteraa, 

 and metasternum, with its epimera and episterna ; these piece- 

 are distinct, except that rarely the epimera and episterna of the 

 mesothorax are entirely united : the form of the epimera of meso- 



