SELECTION OF COLOUR 
593 
Ganoris rapae asleep upon a yellow Dahlia; it was fairly concealed. 
I could not find any other specimens. Again, in the same place a 
week later, I found a male G. napi asleep on a greyish-white corymb 
of Hydrangea; it was extremely cryptic so far as colour was concerned. 
Many years ago the late Mr. Geo. Norman and myself took a lot 
of Folia chi, Linn., at rest close to the hydropathic establishment at 
Forres, and we were much puzzled by the fact that, while many were 
taken on whitewashed walls, where they were difficult to detect, 
quite as many were found resting on dark tree-trunks and could be 
easily seen at many yards' distance. Can this indifference to back¬ 
ground be accounted for by distastefulness ? Or is the species only 
learning to take advantage of the artificial white background ? 
In the Baghi Forest, near Simla, I was struck by the way in 
which the conspicuous yellow Teria$ hecabe , Linn., disappeared when 
it settled on a low shrub with oval leaves fading to a yellow tint, 
the rounded form of the wings aiding its concealment. 1 But the 
most convincing case that up to that time had come under my own 
observation was a large yellow butterfly (I had no net, but think it 
was probably Catopsilia catilla , Cram.) which I saw in the garden of 
the University of Bombay. I saw this settle again and again, 
invariably on a small shrub with yellow leaves. The very con¬ 
spicuous fly would vanish suddenly, and it was only after several 
attempts that I succeeded in catching sight of it when settled, so 
strong was the protective resemblance (February 10th, 1904). 
It is a singular coincidence that on passing through the garden 
of the University of Bombay, March 22nd, 1908, I again saw a 
Catopsilia and watched it settle on a shrub ; this was not a yellow¬ 
leaved plant, as on the former occasion, but its leaves varied a good 
deal in colour, and the butterfly settled on the yellowest; it was 
certainly much less conspicuous than it would have been on the 
greenest leaf. A German fellow-traveller whose attention I called to 
the butterfly agreed as to the partial concealment by the similarity 
in colour. 2 
In an analogous South African case I am able to supply fuller 
details:— 
Eronia, deodor a, Hiibn., is a common Natal Pierine. Few insects 
are more conspicuous in the net than this beautiful fly with its 
combination of creamy-white, jet black, and deep yellow, and one 
might well wonder how it could possibly manage to hide itself. I 
watched it settle once upon the ground, and strangely enough it was 
not conspicuous when its wings were closed and the brilliant yellow 
1 See above, p. 46. 3 See above, p. 94. 
2 Q 
