iq8 ANIMAL LIFE 



accomplished their descent, victors and vanquished clip 

 off their wings and die. 



Butterflies exhibit a similar, though apparently less 

 severe, selection of their mates. Entomologists well 

 know the attractive influence that a single insect will 

 exert over a whole district. By confining a female 

 moth in a wire cage they find that in some strange 

 manner males of that species, even if uncommon or 

 rare in that district, will discover the captive, assemble 

 round her, eagerly vie with one another in striving 

 to win her favour, and, whether by sheer push and 

 vigour, or by some aesthetic consideration, or perhaps 

 by some choice of which we have no conception, one of 

 the competitors is ultimately successful. 



It may be urged that such methods are the excep- 

 tion, and that in the majority of cases there is no 

 evidence of such tourneys or of such toilsome routes 

 being performed before the favour of the mate is 

 won. It might be thought that a large number of 

 animals, such as snails and crabs, are incapable of 

 such ardour, and that in any case such a meticulous 

 care for the colour, agility, or strength of the mate 

 would be misdirected energy, since in point of fact any 

 weaklings would be destroyed by natural causes before 

 the mating season. Recent observations have tended, 

 however, to emphasise the severity of the test that 

 most, if not all, male animals undergo ; and even if 

 we admit that there are many cases where tourneys 

 are not fought before assent is won, yet that it is not 

 by ' natural causes ' that weaklings are weeded out is 



