326 Mr. Westwood’s Remarks on the Thorax of Insects. 
Arr. XLV. Observations upon the Eighteenth Number of 
the Zoological Journal. By J. O. Wrsrwoop, Esq., 
F.L.S., &e. 
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- 
able 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. MacLeay 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 Familles Naturelles, p. 259. “ Le 
“« thorax des Hymenoptéres a abdomen pedicule et celui des Diptéres a 
** une composition particuliére, il est fermé postérieurement par le 
*« prémier segment de l’abdomen, celui que jiai nomme (Mém. du Mus. 
‘< d’Hist. Nat. tom. 7.) mediaire, de sorte que des segments suivants, celut 
“* qui parait étre le premier de cette partie du corps, est réellement le 
« second.’ Such also is the opinion of M, Audouin, as he himself 
recently informed me in Paris; and indeed M. M. Cuvier, Lacépéde, 
and Dumeril in their Report, dated 19th February, 182], upon that 
gentleman’s Researches mention this, as ‘“ une observation curieuve 
‘© de l’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 inyesti- 
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 
Annulosa. The examination of the Earwig is sufficient to convince any 
