2")8 ANATOMY. 



the mesophragma. Another, which may be called the withdrawer, 

 goes from the lower margin of the prophragma to the wings ; 

 passing in its course closely to the exterior margin of the meso- 

 phragma, it assists to expand the wings, and at the same time 

 draws the mesothorax closer to the metathorax. Another holder of 

 the mesosternum, corresponding with that of the mesonotum, originates 

 from the posterior wall of the furcate process, and passes to its an- 

 terior portion upon the metasternum. (Le pretracteur de V apophyse 

 episternale posterieure of Straus.) 



The muscles of the metathorax are considerably larger. They may 

 be considered as the stem of the entire trunk of the beetle, to which 

 the other parts are all attached. It is thence that the true muscles of 

 the metathorax serve only for its own consolidation and strength, and 

 not for its connexion with other parts. 



The largest and strongest of all is the dorsal muscle (musculus 

 metanoti, Vabaisseur de I'aile of Straus), a thick powerful fleshy 

 bundle, which passes from the entire mesophragma to the metaphragma. 

 It falls properly into two halves, one of which belongs to each side of 

 the thorax, but both join together at the central line. 



The lateral dorsal muscles (mitsculi laterales metanoti, les pretrac- 

 teurs de I'aile of Straus) do not much yield in size. These originate 

 from the lateral portion of the metanotum, descend obliquely to the 

 metaphragma, and thus consolidate the dorsal plates. 



The third connecting muscles of the metathorax run from the sides 

 of the metanotum to the side of the metasternum, but so that they 

 originate at the anterior margin of the metanotum, in front of the last- 

 named muscle, and pass obliquely to the posterior lateral part of the 

 sternum, and, consequently, to the cavity of the posterior legs. They 

 are divided into several bellies lying contiguously, all of which closely 

 unite the dorsal plate and sternum together, and, by their contraction, 

 they appear very much to promote respiration. I call them the lateral 

 muscles of the metathorax. They are what Straus calls les elevateurs 

 de I'aile. 



We have already mentioned one muscle connecting the meta- with 

 the mesothorax. Besides which, we find thin prismatical muscles, 

 which, originating at the furcate branches of the internal process of the 

 sternum, pass transversely to the sides of the dorsal plates, and thereby 

 uuite it still more strongly with the sternum. They encompass below 

 the intestinal canal and above the straight dorsal muscles, and insert 



