238 Heredity. 



flies, and it is found over almost the whole of temperate 

 North America. In New England and New York the 

 sexes are alike, but south of lat. 42 some of the females 

 are black, and they are so different from the yellow male 

 and the northern yellow female, that they were for a 

 long time regarded as a distinct species, and have re- 

 ceived a specific name, Papilio glaucus. Between lat. 

 42 and lat. 37 both forms are found, and Prof. Uhler 

 of Baltimore, has reared the yellow female Papilio 

 turnus, and the black one, P. glaucus, from the same 

 lot of eggs, but further south only the black female is 

 found, although the male is exactly like that which in 

 New England is associated with the yellow female alone. 



Wallace has recorded a number of similar cases among 

 the Malayan Papilionidce, of which Papilio Memnon 

 is one of the most striking. In this species there are 

 two kinds of females, one closely resembling the male, 

 and the other differently colored, and furnished with 

 long spatulate tail-like elongations of the hinder wings. 

 These tails are not present on the wings of the male nor 

 on those of the second female, although they are found 

 in both sexes of other species of Papilio, and in some 

 other less specialized genera of the Papilio family. The 

 males, the tailed and the tailless females have all been 

 reared from a single group of eggs, so there is no doubt 

 that they all belong to the same species. 



Wallace has given other cases in which the same male 

 form is found associated, in different countries, with 

 their three different female forms. 



It is possible, and indeed probable, that in some of 

 these cases certain females have resembled the male, 

 while others have either remained unmodified or else 

 have reverted back to an ancestral form. 



Darwin refers to a case of sexual dimorphism which 



