THORAX OF THE BLOW-FLY. 17 



But in order to do this we must first decide any disputed ques- 

 tions that may arise as to the limits of the thorax in these two 

 orders. I believe that as regards the Lepidoptera there is no 

 dispute as to the limits of the metathorax. In Liparis salicis 

 (PL II. fig. 9), behind the lozenge-shaped scutellum of the meso- 

 thorax, we find the metathoracic scutum visible as a triangular 

 space on each side, the mesothoracic postscutellum and the 

 metathoracic prsescuturn both being developed inwardly ; this 

 is followed by a minute scutellum and postscutellum, the latter 

 also developed inwardly. Thus it will be seen that though of 

 considerably less extent than the preceding segment, the meta- 

 thorax has still a very appreciable breadth to correspond with its 

 wing-development. Turn we now to the Hymenoptera. Here 

 we are at once met with an old and hotly-disputed controversy. 

 Audouin* and Latreille* believed that the posterior portion of 

 the thorax in this order is not strictly thoracic — that is, that a 

 portion of the fifth segment of the body entered into its com- 

 position ; while Macleayt was of opinion that the said portion 

 was the scutellum of the metathorax enormously enlarged ; and 

 WestwoodJ seems also to have regarded it as thoracic §. I do 

 not know that this question is regarded as settled even now, 

 although the view taken by Packard || is, so far as concerns the 

 Hymenoptera, similar to Audouin's and my own ; and I think the 

 balance of opinion inclines that wayH. It will be evident, how- 

 ever, on a little consideration that the decision of this question 

 must largely affect the course of our reasoning, for if we adopt 

 Macleay's views we shall have in the Hymenoptera a metathoracic 

 development out of proportion to that of the posterior wings. I 

 will therefore advance a few arguments to show that in this 

 matter Audouin and Latreille are right as opposed to Macleay ; 

 and in the first place draw attention to the two figures illustra- 

 ting different stages of the development of the pupa of the 



* See Westwood's ' Introduction,' vol. ii. p. 75. 



t Zoological Journal, vol. v. p. 172. \ Tom. cit. 



§ Burmeister and Newport were also opposed to Audouin on this point. See 

 Shuck. Transl. Burm. p. 235, and Newport's "Insecta," Todd's Cycl. Anat. and 

 Physiol, p. 55. 



|| Packard's Guide to the Study of Insects, pp. 67 & 109. 



% Subsequent to the reading of this paper, I have noticed that Sir John Lub- 

 bock and Dr. Eatzeburg take the same view. See abstract, "The Anatomy of 

 Ants," Journ. Linn. Soc, Zool. (No. 80), vol. xiv. p. 738. I may also quote H. 

 Eeinhard as supporting a similar view, vide Berlin, entom. Zeitschr. 1865, p. 207. 



