154 THE THEORY OF EVOLUTION 



temperature. Some very striking changes were 

 produced in this manner and the remarkable case of 

 the Lunar Moth, taken from Texas to Switzerland, 

 has already been described in another connection. 

 (See p. 39.) Cocoons of one species of butterfly 

 and one moth, when exposed to a low temperature, 

 considerably below the freezing point, yielded mature 

 insects which, especially in the males, were darker in 

 colour and had a different wing-pattern from those 

 which were hatched at normal temperatures. The 

 second generation, derived from these modified 

 parents, but hatched from cocoons exposed to the 

 normal temperature of the season, had a consider- 

 able number of insects which resembled their dark 

 parents, while others had reverted to the ordinary 

 condition of the species. In another moth a very 

 decided darkening of the wings and a change of 

 pattern was produced by the opposite method of 

 keeping the cocoons in an atmosphere much hotter 

 than that of the hatching season out of doors. Here 

 also a considerable number of moths in the second 

 generation inherited the characters of their modified 

 parents, though they themselves had been hatched 

 at the normal temperature. The larvae of a beetle, 

 which feed upon a smooth-leaved willow, were 

 transferred to another species with densely hairy 

 leaves. The descendants freely chose the hairy 

 leaves, when both kinds were accessible and the 

 number so choosing increased with each successive 

 generation, the effect being cumulative. 



