436 Mr. Poulton's/(t/-f/<cr experiments rqion 



4. Experiments in 1888 upon the pup.e of Vanessa 

 polychloros. 



Two larvsB, found near Oxford, were subjected to experi- 

 ment at the end of July, the pupae being compared 

 July 31. The larvae passed all three stages preparatory 

 to pupation under the conditions described below. 



One had been placed in a moderate-sized cylinder, 

 covered externally with two thicknesses of black tissue- 

 paper and a roof of the same (IX). This being inverted 

 on a black paper floor, was in almost complete darkness. 

 The pupa (position unnoted) was much darker than the 

 other, with no trace of the gold spots. It was com- 

 parable to a dark (3) of Vanessa nrticce. 



The other was placed in the gilt compartment (XXXI.), 

 and was fixed to the roof. Compared with V. urtica it 

 would be a light (3). The gold spots were present on the 

 metathorax and 1st and 2nd abdominals, although they 

 were not vei'y bright, and there was no tendency to 

 spread over the general surface, as is so commonly the 

 case with the brighter forms of T'. urticce. 



My friend Mr. 0. H. Latter also experimented on the 

 same species in 1888, and sent the pupfe to me for com- 

 parison, which took place August 15. 



Three pupae, formed in black surroundings in a dim 

 light, were nnich darker than the others, with no trace of 

 metallic spots. 



Three pupae, formed in gilt surroundings in a strong 

 light, were all light varieties, with silver spots on the 

 three usual segments. 



The results were very uniform in both sets, and the 

 difference greater than in my experiment. It is likely 

 that the dimly illuminated dark surfaces produce more 

 effect than the same in darkness. This is shown in 

 many experiments on other larvae and pupae recorded in 

 this paper. 



For a much longer series of experiments made in the 

 same year bv the Rev. J. W. B. Bell, see ' Midland 

 Naturalist,' December, 1889, pages 289-90. These 

 results also show a very high degree of sensitiveness in 

 the species. The colours appear to be such as to afford 

 concealment, especially upon irregular dark surfaces of 

 bark or rock. 



