Thorax in winged Insects. 177 



Terguin of Prothorax .... 4 

 Pectus of Prothorax .... 6 



Tergum of Mesothorax * ... 4 



Paraptera 2 



Pectus of Mesothorax .... 6 



Tergum of Metathorax ... 4 



Paraptera 2 



Pectus of Metathorax .... 6 



Total . 34 

 which, if the simple pieces, as sternum, scutellum, &c. be reckoned as 

 composed of two, joined by the medial line, will make 52 pieces com- 

 posing the thorax.f Of these Mr. Kirby does not describe much more 

 than 20, and yet uses about 40 different words for them in his nomencla- 

 ture of the parts of the thorax. On the other hand, the nomenclature 

 given in this paper, and which I have borrowed from M. Audouin with 



• If I am right as to the separate existence of the lateral pieces of the scu- 

 tum of the mesothorax, which I call parapsides, then, of course, the tergum 

 of the mesothorax is composed of six pieces, four longitudinal, and two late- 

 ral. These last two pieces may he occasionally detected separate in the other 

 orders, but in all they are very usually confluent with the scutum of the me- 

 sothorax, so as to form one piece with it. Vestiges of the separation, however, 

 occur even in Polistes, Scolia, &c., and they become perfectly distinct in Ckal' 

 cis, &c., although in the neighbouring genus Leucospis, they are completely 

 confluent. Perhaps the parapsides are the two pieces which, added to M. 

 Audouin's, complete the number which M. Jurine assigns to the thorax. M. 

 Jurine had studied the subject too deeply not to have had good reasons for giv- 

 ing this number of pieces to the thorax, although, unfortunately, his lamented 

 death prevented him from naming them. 



f Considering the sternum at its maximum of developement, which I believe 

 it never is in Hymenoptera, it will consist of four transverse segments which, 

 when divided by the medial line, will make the whole number of pieces in the 

 thorax mount up to about 72. But I do not believe that ever this whole num- 

 ber of pieces can appear together in any insect, because the developement of 

 one will cause one or more of its contiguous ones to disappear. 



Vol. V. M 



