THORAX. 263 



the thorax, which in the larva state were but equal in size to 

 the remaining segments : hence we find that the thorax in 

 the perfect insect has become the most robust, yet compact, 

 as well as the most complicated in its structure, of all the 

 body-segments of an insect. Moreover, the great diversity 

 in the organization of the wings, and the occasional transfer 

 of wing motion to a single pair of wings, this pair being 

 either the anterior, as in the Diptera, or the posterior, as in 

 the beetles, have necessitated a concurrent modification in 

 the form of the thoracic segments according therewith, as 

 well as similar modifications resulting from the varying mo- 

 tions of the legs. 



Figs. 116, upper, and 117, under side of the thorax of a beetle (Buprntis) : T 1, pronotum 

 (T) l.prosternum; T 2, laesonotum ; (T) 2, mesosteruum.uiarked ivith lines to distinguish 

 its boundary ; T 3, metanotnm ; (T) 3, metasternum ; H,head; A, abdomen ; w 1, elytra; 

 w 2, posterior wings. 



It is further to be noticed, that the many parts of which 

 the thorax is thus composed, were provided by entomologists 

 with separate names, whereby the nomenclature of this part 

 of the body has become very complicated, more especially as 

 the same part has received more than a single name, accord- 

 ing to the greater or less degree of its developement. This 

 has been more particularly the case ir the " Introduction to 



