THE THORAX. 87 



78 a. 



After having thus explained the construction of the thorax in the 

 different orders of insects, it remains for us now to notice the works 

 of other naturalists upon the same subject, and to indicate the differ- 

 ence of the results of their investigations. 



The earliest work of this kind is that of Chabrier ; it appeared as 

 the introduction to his treatise upon the flight of insects *, which was 

 presented to the academy of Paris on the 28th of February, 1820. He 

 here, with Latreille, divides the thorax into protliorax, mesothorax, 

 and metatliorax, but unites the two last divisions as tronc alifire. 

 Each of these segments is subdivided into the upper, or DORSAL, and 

 under, or PECTORAL, part ; called also conque pectorale, from which 

 processes, the entosternum, spring inwards. Between both, upon the 

 metathorax, are found the clavicules thoraciques ; and upon the meso- 

 thorax, the plaques fulcr ales. The partitions, or phragmae, he describes 

 as prce- and post-dorsum ; and he calls the scutellum, bascule. He 

 consequently adopts as many pieces as we have described : the annexed 

 table will show more distinctly their conformity. 



Chabrier was succeeded by Audouin in a similar investigation, in 

 which, however, the chief object was the particular description of the 

 sternum. This was also presented to the academy, and a report of it 

 was given by Cuvier, in the Annales Generales de Physique, torn. vii. 

 (1821 f ). He has here adopted, in general, the same parts; but each 

 single one is divided into several pieces, with particular names, although 

 such pieces are never found separated from each other. It may also 

 be objected to Audouin's performance, that he has not distinguished 

 the several dorsal and pectoral plates of the three segments by distinct 

 names, but has merely called them terga and pectora. We cannot, 

 therefore, retain his nomenclature. But Audouin admits of three seg- 

 ments, which he calls pro-, meso-, and meta-thorax ; each consists of 

 tergum, episternum, sternum, and entothorax ; to which are added, in 

 the prothorax, the trochantinus and the peritrema ; in the meso- 

 thorax, the peritrema and paraptera ; and in the metathorax, the 

 parapterum only. Each tergum consists of the preescutum, or the 

 anterior deflexed margin, which, in the mesonotum, becomes the pro- 



* Essay sur le Vol. des Insectes. Paris, 1 832, 4to. 



t Audouin himself published the paper in the Annales des Sciences Naturelles, torn. i. 

 p. 97, and p. 416. 



