424 Mr. F. Merrilield and Mr. E. B. Poulton on 



1887, I. c, and Trans. Ent. Soc. Lond. 1892, /. e.: see also 

 G. C. Griffith's experiments on this species in Trans. 

 Ent. Soc. Lond. 1888, p. 247.) 



It is interesting to observe the relation between the 

 effects of darkness (4) and those of clear glass (14). The 

 latter produced even darker pupse relatively to the former 

 than in the case of F. hrassiae. 



The table does not support Mr. Merrifield's conclusion 

 that the yellow (9, 10, 11) was less effective than in the 

 case of P. hrassicm. The six pupae were of the two lightest 

 degrees, four of them green and the other two greenish. 



The effect of the green and orange screens (7, 13) is 

 confirmatory of previous results with other species (F. 

 IrassiciB and V. io). 



It is not necessary to comment further upon the other 

 results, all of which will be clear upon an inspection of the 

 table on p. 423. 



iT.— EXPERIMENTS UPON THE PUP^ OF 



Vanessidx. 



1. Experiments upon the Pup^ of Vanessa urticx and 



Fyrameis cardui. (C. B. S. and E. B. P.) 



In the course of our investigations in 1898 into the 

 struggle for existence during the pupal period of Vanessa 

 urticai it was necessary to produce a very large number 

 of pupae with colours as widely contrasted as possible. In 

 order to achieve this we made use of black surroundings 

 on the one hand and gilt (Dutch " gold "), yellow, orange, 

 and white on the other. There was abundant evidence in 

 the 700 pupas which we obtained of the previously recorded 

 influence of these surroundings, and also, to our frequent 

 annoyance, of the effect of the dark surfaces of the larvae 

 upon one another. In fact so powerful was this influence 

 and so gregarious were tlie larvae under the conditions of 

 our experiments that intermediate pupas were generally 

 produced when the lightest forms were desired. The con- 

 ditions of the investigation rendered it impossible to isolate 

 so many larvae in separate cases. 



Many of the larvae pupated on the leaves and stems of 

 the food-plant (nettle), and when isolated brilliant golden 

 pupas were almost invariably produced. 



A few larv« of P. cardtii were also found and subjected 

 to black and white surroundings : the pupae being dark in 

 the one case, and light, and often brilliantly metallic, in 

 the other. 



