288 THE COLOURS OF ANIMALS 



can only be settled by careful observation under the 

 most natural conditions. This conclusion is rendered 

 probable by the following considerations. 



The female of the Emperor Moth (Saturnia carpini) 

 is so eagerly sought by the males, that when a virgin 

 female is taken into a favourable locality the collector 

 is soon surrounded by troops of males which have 

 been guided by a marvellously delicate sense of smell 

 residing in their branching antennae. So delicate is 

 the sense that the female is recognised perhaps miles 

 away, and recognised as a virgin. Directly mating 

 takes place the other males disappear. In this case 

 selection chiefly, if not entirely, tends to improve the 

 sense of smell in the males and the mode and rapidity 

 of their flight. The mode of flight is probably im- 

 portant in enabling the insect to cover as wide a 

 volume of air as possible while it advances, and thus 

 to stand a greater chance of crossing some thin 

 stratum or current of air in which the odoriferous 

 particles are contained. To such a selective process 

 we must ascribe the wonderful antennae of these 

 males and their peculiar and rapid flight. Since, 

 however, both males and females are very beautiful, 

 the males possessing the brighter colours, this 

 example seems at first sight to support Mr. Wallace's 

 views. I shall endeavour to show that the facts are 

 capable of an opposite interpretation. I have here 

 called attention to the habits of the species, because 

 it is nearly allied to Bombyx cynthia, and because the 



