Chap. XI. 
BUTTERFLIES AND MOTHS. 
399 
the males have the hind-wings whiter than those of 
the female — of which fact Agrotis exclamationis offers a 
good instance. The males are thus rendered more 
conspicuous than the females, whilst flying about in 
the dusk. In the Ghost Moth (. Hepialus humuli ) the 
difference is more strongly marked; the males being 
white and the females yellow with darker markings. 
It is difficult to conjecture what the meaning can be 
of these differences between the sexes in the shades of 
darkness or lightness ; but we can hardly suppose that 
they are the result of mere variability with sexually- 
limited inheritance, independently of any benefit thus 
derived. 
From the foregoing statements it is impossible to 
admit that the brilliant colours of butterflies and of 
some few moths, have commonly been acquired for the 
sake of protection. We have seen that their colours 
and elegant patterns are arranged and exhibited as 
if for display. Hence I am led to suppose that the 
females generally prefer, or are most excited by the 
more brilliant males ; for on any other supposition 
the males would be ornamented, as far as we can 
see, for no purpose. We know that ants and certain 
lamellicorn beetles are capable of feeling an attachment 
for each other, and that ants recognise their fellows 
after an interval of several months. Hence there is no 
abstract improbability in the Lepiaoptera, which pro- 
bably stand nearly or quite as high in the scale as these 
insects, having sufficient mental capacity to admire 
bright colours. They certainly discover flowers by 
colour, and, as I have elsewhere shewn, the plants 
which are fertilised exclusively by the wind never have 
a conspicuously-coloured corolla. The Humming-bird 
Sphinx may often be seen to swoop down from a distance 
on a bunch of flowers in the midst of green foliage ; 
