Chap. XL 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 (Hejnalus 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 Lepidoptera, 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 } 



