402 



MY LIFE 



[Chap. 



ornamented with white bands or spots. These are excessively 

 abundant, and, having few enemies, they fly slowly. Now 

 there are also several different kinds of papilios, which in 

 colour are so exactly like these, that when on the wing they 

 cannot be distinguished, although they frequent the same 

 places and are often found intermingled. Other protected 

 butterflies are of paler colours with dark stripes, and these 

 are also closely imitated by other papilios. Altogether there 

 are about fifteen species which thus closely resemble pro- 

 tected butterflies externally, although in structure and trans- 

 formations they have no affinity with them. In some cases 

 both sexes possess this resemblance, or mimicry,'* as it is 

 termed, but most frequently it is the female only that is thus 

 modified, especially when she lays her eggs on low-growing 

 plants ; while the male, whose flight is stronger and can take 

 care of himself, does not possess it, and is often so different 

 from his mate as to have been considered a distinct species. 



This leads us to the phenomenon of dimorphism and 

 polymorphism, in which the females of one species present 

 two or three different forms. Several such cases occur in the 

 Malay Archipelago, in which there are two distinct kinds of 

 females, sometimes even three, to a single male, which differs 

 from either of them. In one case four females are known to 

 one male, though only two of them appear to occur in one 

 locality. These have been almost always described as 

 distinct species, but observation has now proved them to be 

 one, and it has further been noticed that each of the females, 

 which are very unlike the male, resembles more or less 

 closely some " protected '* species. It has also been proved 

 by experimental breeding that eggs laid by any one of these 

 females are capable of producing butterflies of all the 

 different forms, which in the few cases recorded are quite 

 distinct from each other, without intermediate gradations. 



The local diversities of form are illustrated by outline 

 figures (as regards two species of papilio from Celebes) in 

 my "Malay Archipelago" (p. 216), and similar local pecu- 

 liarities of colour, both in papilio and other groups, are 

 described in my Natural Selection and Tropical Nature " 



