440 Mr. Foultons further experiincnts upon 



under tins degree in 1887 (Phil. Trans., B., I.e.), and 

 they had a greater development of the black patches, 

 and a more dusky appearance over the whole surface. The 

 opaque whitish yellow band crossing the 8rd abdominal 

 was slightly marked or absent, and the green ground- 

 colour was not so deep in tint. 



The whole of the experiments are described in the 

 following table : — 



{See Table, pages 441, 442, 443, 444, 445.) 



A more exact statement of the light transmitted 

 through the screens and reflected from the backgrounds 

 will be given in F. Conclusions, where the main results 

 of all such experiments will be compared together. 



It is very unfortunate that these experiments on the 

 Picridce, which were conducted with the greatest care, 

 should have lost much of their value from the death of 

 so great a majority of the larvffi. With five times as 

 many individuals to argue from — and this was the num- 

 ber introduced into the cases -tolerably safe conclusions 

 might have been drawn. Even as it is, the conclusions 

 are probably reliable, harmonizing as they do with those 

 derived from the investigation of V. io. 



In the latter species, and in the Pieridce in 1886, it 

 was ascertained that the larvce are sensitive to the orange 

 and yellow rays reflected from the adjacent background, 

 when diluted with other rays from the same source, and 

 an immense preponderance of direct white light. But 

 in the case of T'. io, it has been shown that when both 

 these causes of dilution are reduced by the use of coloured 

 screens, the larvae became sensitive to reflected rays 

 which would not ordinarily affect them, viz., from the 

 red rays beyond the orange, and the green beyond the 

 yellow ; but blue light, however concentrated, did not 

 appear to affect them. 



Let us now apply this conclusion to the experiments 

 described above. 



Red glass in front of white and orange paper j)roduced 

 a far greater effect in the direction of green pupse than 

 is usually produced by red paper in white light. 



Yellow (/lass, in front of backgrounds which reflected 

 the yellow light, produced much the same effects as 

 yellow backgrounds in strong light; in front of non- 

 reflecting backgrounds it produced darker pupae. 



