326 Mr. Westwood's Remarks on the Thorax of Insects. 



Art. XLV. Observations upon the Eighteenth JWmber of 

 the Zoological Journal. By J. O. Westwood, Esq.^ 

 F.L.S., S^c. 



to the editor of the zoological journal. 

 Sir, 



My attention having been in an especial manner directed by Mr. Mac 

 Leay in the last number of this Journal, (p. 178), to the comparative 

 structure of the thorax of the genera of Insects, I beg leave to assure you 

 that so interesting and important a subject has not been overlooked in the 

 course of my entomological investigations. There is, however, a remark- 

 atle opinion entertained by the French Scavans relative to the typical 

 structure of the terminal portion of the Metathorax of the Hymenoptera, 

 which, upon being informed that Mr. Mac Leay was engaged upon that 

 subject, I had hoped would have been subjected to his scrutinizing inves- 

 tigation ; I cannot therefore but regret that he was not aware of the opinion 

 referred to, otherwise he would doubtless have noticed it. I find the 

 following observation in Latreille's Families Naturelles, p. 259. " Le 

 " thorax des Hymenopteres a abdomen pedicule et celui des Dipteres a 

 " une composition particuli^re, il est ferme posterieurement par le 

 " premier segment de I'abdomen, celui que jiai nomme (Mem. du Mus. 

 " d'Hist. Nat. torn. 7.) mediaire, de sorte que des segments suivants, celui 

 " qui parait etre le premier de cette partie du corps, est r^ellement le 

 " second." Such also is the opinion of M. Audouin, as he himself 

 recently informed me in Paris; and indeed M. M. Cuvier, Lacep^de, 

 and Dumeril in their Report, dated 19th February, 1821, upon that 

 gentleman's R<isearches mention this, as " une observation curieuve 

 " de I'auteur" p. 11. 



Why does not M. Audouin enlighten the students of comparative 

 anatomy, by the publication of his very numerous delineations and 

 descriptions relative to the structure of the thorax of the various orders? 



The student should also direct his attention to the anatomical investi- 

 gations of M. Srauss upon the Cock Chaffer and Hornet. 



Intimately connected with the question of the typical formation of 

 the thorax is that relative to the typical number of segments in the 

 ./Jnmilnsa. The examination of the Earwig is sufficient to convince any 



