1S78.] 59 



ON THE PUPATION OF THE NYMPEALIBM. 

 BY J. A. OSBOEXE, M.D. 



Last year I commimicated to " iS'ature " (vol. xvi, pp. 502-3) a 

 discovery of mine iu regard to this matter ; and as my explanation 

 of the process is altogether at variance with the account given in 

 Kirby and Spence, and other works of the kind, I expected that it 

 would have called forth some reply. As I have no access to any books 

 here but my own, I should not have been surprised to hear that my 

 discovery had been anticipated, or was even a fact well known to 

 entomologists, as it is by no means far to seek or difficult to verify. 



In watching the transformations of Vanessa urticcd, I found that 

 the chrysalis was attached to the old skin of the caterpillar by a mem- 

 brane sufficiently strong and permanent to support the insect during 

 the critical last moments of pupation, and fully explaining why it does 

 not fall down when the tail of the chrysalis is withdrawn from the 

 old skin and thrust up to be attached to the silk. I found the same mem- 

 brane, only less perfect, in the common white butterily, and I believe 

 I have evidence of it also in some beetles. It is now the time when 

 the matter can be easily investigated in Vanessa and its congeners of 

 the Suspensi ; and I would, therefore, request you to call attention to 

 it in your magazine, or if the thing is already known, that you would 

 kindly inform me of the fact. I have still some of the specimens 

 prepared last year to show the membrane in situ, and will be happy to 

 forward them for inspection, if required. I may say that I bought 

 some books treating of the metamorphoses of insects, with the hope of 

 clearing up this matter, but have hitherto failed to obtain any in- 

 formation on the subject. 



Milford, Letterkenny : 



2Uh June, 1878. 



[We reprint below the letter to "Nature," referred to by our 

 correspondent, and will be very glad to know if the very reasonable 

 explanation advanced in support of his theory has been elsewhere 

 referred to, and also to have the results of direct experiment by 

 others. So far as we can discover, most of the published accounts are 

 simply copied, or extracted, from Heaumur. That most original of 

 British entomologists — George Newport — in the article " Insecta,^^ in 

 Todd's Cyclopaedia of Anatomy and Physiology, vol. ii, pp. 876, 877, 

 gives a much detailed account of the method of pupation of Vanessa 

 urticcB, but misses all mention of the critical moment when the tail of 

 the chrysalis is withdrawn from the cast-off larval skin ; and our valued 



