I go DARWINISM AND THE PROBLEMS OF LIFE 



dark corners and crevices in which they rest. The 

 colours of large and small tortoise-shell butterflies and 

 the painted lady are lighter. They usually sit on the 

 road, and seem to disappear suddenly after one has 

 been watching the flying, prettily-coloured insects. 



The disposal of the wings is different in the night- 

 lepidopters. With these the fore-wings cover the hind 

 ones roof-wise, and so we often find very light colours 

 on them — as, for instance, in our red underwings or 

 tiger-moths — and never on the fore-wings, which alone 

 are visible when they are resting. On these there is 

 a mixture of different colours, with zigzag streaks and 

 lines running between them ; the whole taken together 

 gives so good a picture of the bark of a tree or a 

 wooden wall that even the experienced naturalist 

 often overlooks one of these moths in examining the 

 trunk of a tree. The intricate design is always the 

 same in every detail, and it has very well been com- 

 pared to an impressionist landscape, in which all kinds 

 of scrawls seem to be thrown together irregularly, 

 though it will be found to be a picture on moving 

 away from it a little. Natural selection easily explains 

 a colour-design of this kind. All variations in the 

 animals are preserved and selected that help on the 

 resemblance to the bark. In one part the zigzag 

 lines were developed, in another spots, in a third the 

 dark ground-colour. As all these selected variations 

 repeatedly crossed with each other, their descendants 

 came to possess the different features together, and 

 steady selection of the combination helped to make 

 the deception more complete. 



