ON COLOURS IN NATURE. 107 
“Jn reading Dr. Walker’s interesting paper on ‘Colours in 
Nature,’ one cannot but be struck by his reference to the prevalence 
of blue. I think this can scarcely be considered to extend further 
than the sky and the sea. The indigo blue, which, no doubt, is the 
favourite colour in the Hast, not only in Egypt, but still more in 
China and Japan, is favoured, I imagine, not so much from the 
‘prompting of a picturesque effect,’ as from the facility with which 
indigo dye can be obtained in those regions compared with the dyes 
for orange or black. 
“Tn insects I do not think that blue can be called a prevalent 
colour ; certainly among the coleoptera it is not so. 
“T can scarcely agree with Dr. Walker in supposing that the 
usually brighter upper side of the wings of butterflies is due to 
more exposure to sunlight. I think that I have seen the “ wlhute 
admiral” butterfly sitting on a bush, alternately raising and lowering 
its wings, and showing a dull black and white upper side and a 
bright red and white under side. The fritillaries, again, are much 
brighter on the under side (adorned, as many of them are, with 
silvery spots), than anything the upper side can show. 
“Concerning the iridescence and variable colouring exhibited by 
some insects, I would observe that, so far as my experience goes, the 
variable colouring in beetles appears to be confined to red and green. 
Of this there is a notable example in a Carabus found in Spain, the 
elytra of which appear, when viewed from one direction, to be of 
an intense coppery red, and, when seen from another point, they 
become a vivid emerald green. Jn some of the cetonide there is a 
peculiarly bright polished appearance, giving the insect an aspect 
of having been covered with liquid.” . 
Mr. F. P. Pascon, F.L.S., writes :— 
“T have read Dr. Walker’s interesting paper, and I can only 
suggest that the alleged fondness of insects for blue flowers might 
have been mentioned, as well as Sir J. Lubbock’s experiments with 
regard to colours in relation to ants. I can confirm Wallace’s 
account of the absence, or rather the scarcity of flowers in the 
forests of the Amazon and other tropical parts of South America. 
Kingsley is also right. In the West Indies, especially in the smaller 
islands, cultivation has displaced much of the arboreal vegetation, 
but I doubt if in any of them anything like the Brazilian forests 
ever existed. Darwin was ‘ most affected by the emotions of the 
