Mr. R. J. Ashton's Note, &;c. 157 



XXII. JVote on the Metamorphosis of Caterpillars. 

 By R. J. AsHTON, Esq., F. L.S. &:c. 



[Read 5th November, 1838.] 



On that interesting part of the physiology of insects, the meta- 

 morjihosis, an extraordinary discrepancy has hitherto existed 

 between the statements of some of the most eminent investigators 

 of this department of creation. I say extraordinary, because, for 

 a matter capable of such easy and satisfactory elucidation as is 

 the subject of this dispute, to have been the theme of such 

 contradictory assertions from a considerable time back down to 

 the present hour, as this has been, cannot but appear extraordi- 

 nary. The point in difference is this : — Swammerdam, the most 

 assiduous and expert Entomologist and one of the acutest ob- 

 servers that perhaps ever lived, made the discovery of a fact, 

 which certainly deserves to be ranked among the most marvellous 

 operations which are exhibited in nature : — viz. that at the same 

 time that the moult of the external integument of the caterpillar 

 takes place, the mucous tunic of the intestinal canal is also stripped 

 off and rejected through the anus, and not only that, but each 

 of the attenuated and delicate ramifications of the air vessels, invi- 

 sible, or nearly so, as they are to the naked eye, sheds its internal 

 lining, which, to the number of some hundreds, are withdrawn 

 through the spiracles, thus leaving the animal completely reno- 

 vated as it were both within and without, with increased capacity 

 or wholly altered form. This observation was corroborated by 

 Bonnet, a naturalist no less celebrated in this branch of science 

 than the former. On the authority of such eminent men the fact, 

 prodigious as it must appear, was generally received, until Herold, 

 a very able physiologist, asserted, that the inner skin of the intes- 

 tinal canal is never cast, and as respects the trachea, such moult 

 is confined to the large main trunks, none taking flace in their 

 smaller ramifications. Thus a complete and irreconcileable dis- 

 crepancy existed between these acute physiologists, the only dif- 

 ference in the nature of the observations, upon which their state- 

 ments were pi'ofessedly grounded, being, that Swammerdam 

 appears to have made his on the larvas of beetles {Oryctes Nasi- 

 cornis, et al.), whilst Herold's appear to have been made on the 

 caterpillars of the Lepidoptera. Later writers on this subject* 

 appear to have been contented to discuss the question on the 



* Kirby and Spence, Burmeister, &:c. 

 VOL. III. N 



