98 THE GENESIS OF SPECIES. [CHAP. 



able varieties from the adjacent islands, of Bouru and New 

 Guinea, it is of a golden yellow, hardly inferior in brilliancy 

 to its color in the male sex. The female of Omithoptera 

 Priamus (inhabiting Amboyna and Ceram exclusively) is 

 of a pale dusk^-brown tint, while in all the allied species 

 the same sex is nearly black, with contracted white mark- 

 ings. As a third example, the female of Papilio Ulysses 

 has the blue color obscured by dull and dusky tints, while 

 in the closely-allied species from the surrounding islands, 

 the faemles are of almost as brilliant an azure blue as the 

 males. A parallel case to this is the occurrence, in the 

 small islands of Goram, Matabello, K6, and Aru, of several 

 distinct species of Euploea and Diadema, having broad 

 bands or patches of white, which do not exist in any of 

 the allied species from the larger islands. These facts 

 seem to indicate some local influence in modifying color, 

 as unintelligible and almost as remarkable as that which 

 has resulted in the modifications of form previously de- 

 scribed." 



After endeavoring to explain some of the facts in a way 

 to be noticed directly, Mr. Wallace adds : " " But even the 

 conjectural explanation now given fails us in the other cases 

 of local modification. Why the species of the Western 

 Islands should be smaller than those farther east; why 

 those of Amboyna should exceed in size those of Gilolo 

 and New Guinea ; why the tailed species of India should 

 begin to lose that appendage in the islands, and retain no 

 trace of it on the borders of the Pacific ; and why, in three 

 separate cases, the females of Amboyna species should be 

 less gayly attired than the corresponding females of the sur- 

 rounding islands, are questions which we cannot at present 

 attempt to answer. That they depend, however, on some 

 general principle is certain, because analogous facts have 

 been observed in other parts of the world. Mr. Bates in- 

 16 "Natural Selection," p. 177. 



