1887.] Mr, Edward B. Puulton on Gilded Chrysalides. 33 



WEEKLY EVENING MEETING, 

 Friday, February 11, 1887. 



SiE William Bowman, Bart. LL.D. F.E.S. Manager and 

 Vice-President, in the Chair. 



Edward B. Poultox, Esq., M.A. 



Gilded Chrysalides. 



Previous Work — Mr. T. W. Wood in 1867 published the obser- 

 vation that certain pupae (Pieris hrassicse, P. rajpse, kc) resemble in 

 oolour the surface on which they are found. Although this was 

 disputed by some naturalists, it was confirmed by Mr. A. G. Butler 

 and Prof. Meldola. In 1874 Mrs. M. E. Barber published 

 some very striking observations on the colours of the pupa of 

 Papilio nireus (South Africa) confirmation being afterwards afforded 

 by Mr. Trimen, from the case of Papilio dernoleus. Dr. Fritz 

 Muller, however, shows that Papilio polydamus is not sensitive to 

 surrounding colours. The observations were explained by supposing 

 the moist skin of the freshly formed pupa to be " photographically 

 sensitive " to the colour of surrounding surfaces ; but Prof. Meldola 

 pointed out that there can be no real analogy with photography. 

 Furthermore, many pupae are formed at night when the surrounding 

 surfaces are dark. The present investigation was undertaken with 

 the belief that the influence would be found to work upon the larva 

 as it rests upon some coloured surface before pupation. 



I. Experiments upon Vanessa lo. — This pupa appears in two varie- 

 ties, being commonly dark grey and much more rarely yellowish-green. 

 Six larvae placed in a glass cylinder covered with green tissue paper, 

 produced six green pupae ; one of these transferred to a black surface 

 while still moist and fresh, became a green pupa precisely like the 

 others. 



II. Experiments upon Vanessa urticse. — The pupae have no green 

 form, but appear in many shades of dark grey, the lighter ones having 

 golden spots on them, while the extreme forms are almost covered 

 with the golden appearance. These latter are very rarely seen in 

 nature, except when the pupa is diseased. Over 700 pupae were 

 obtained in the following experiments : — 



1. Effects of Colours. — Gh-een and orange surroundings caused no 

 effect on the pupal colours ; hlach produced, as a rule, dark pupae ; 

 u'hite produced light pupae, many of them being brilliantly golden. 

 This last result suggested the use of gilt surroundings, which were 

 found to be more efficient than white, and produced pupae with a 

 colour which even more resembled gold. 



2. Mutual Proximity. — The larvae being dark, it was found that 

 when many of them became pupte on a limited (white or gilt) area, the 



Vol. XIL (No. 81.) d 



