88 PARTIAL ORISMOLOGY. 



phragma, and, in the metanotum, the mesophragma ; the scutum, the 

 disc of each dorsal plate ; the scutellum, or the posterior margin; and 

 the postscutellum, the posterior deflexed margin, which, in the meso- 

 notum, becomes sometimes the mesophragma, or, upon the metanotum, 

 it forms itself into the metaphragma. Upon the prothorax, the epister- 

 num and the epimeruin form our omium : the former is the exterior 

 surface ; the latter the interior surface, directed towards the acetabula. 

 Where the shoulder- piece is not free, they then belong to the pronotum, 

 and form the lateral parts. The trochantinus by no means belongs to 

 the thoracic case, but to the coxae ( 168, II. 4) ; the same applies to 

 the peritrema, which forms the corneous ring of the spiracle. The 

 entothorax is what we shall describe below ( 165) as the processus 

 internus sterni ; it is in strict union with the sternal plate, and is 

 never free or separated from it. I do not distinctly know what the 

 parapterum is ; probably a lateral process of the dorsal plate. I have 

 never found a free portion in that situation. In the mesothorax, the 

 episternum and epimerum are our scapulae : but upon the metathorax, 

 the parapleurse. 



After Audouin, Straus-Durckheim * and Macleay f both produced, 

 nearly about the same time, a work upon the thorax of insects : the 

 description of the latter adheres very closely to that of Audouin. 

 He uses the same names and adopts the same parts ; but in his sub- 

 division of them, he goes still further, without there being a sufficient 

 reason for it. For example, the sternal plates of the meso- and meta- 

 thorax, he says, consist each of eight pieces, although in no insect with 

 which I am acquainted is there the least indication of any other sepa- 

 ration than the above-adduced division into two halves. 



Straus-Durckheim pursues in his description of the thorax, as well 

 as throughout his work, a peculiar path, without troubling himself in 

 the least about the labours of his predecessors. He divides the whole 

 thorax into corselet and thorax, the latter comprising that portion 

 which bears the wings ; this is again divided into prothorax (our 

 mesothorax) and metathorax. The corselet consists of the bouclier, 

 our pronotum ; the two pubis, the rotule, Audouin's trochantinus, 

 and the sternum antcrieure. He distinguishes in his prothorax the 

 ecusson, our mesonotum,, the clavicule anterieure, Audouin's para- 



" Consid. Gen. sur TAnat. comp. des Alii. Articiil. Par. 1828, 4to. p. 76, &c. 

 f Zoological Journal, Vol. v, (1830), No. 18, p. 145. 



