SEXUAL SELECTION 589 



enbation, have not had their bright colors eliminated through 

 natural selection, the males often differ in a slight, and occa- 

 sionally in a considerable, degree from the females. This 

 is a significant fact, for such differences in color must be 

 accounted for by some of the variations in the males having 

 been from the first limited in transmission to the same sex; 

 as it can hardly be maintained that these differences, espe- 

 cially when very slight, serve as a protection to the female. 

 Thus all the species in the splendid group of the Trogona 

 build in holes; and Mr. Gould gives figures" of both sexes 

 of twenty -five species, in all of which, with one partial ex- 

 ception, the sexes differ sometimes slightly, sometimes con- 

 spicuously, in color — the males being always finer than the 

 females, though the latter are likewise beautiful. All the 

 species of kingfishers build in holes, and with most of 

 the species the sexes are equally brilliant, and thus far 

 Mr. Wallace's rule holds good; but in some of the Aus- 

 tralian species the colors of the females are rather less vivid 

 than those of the male ; and in one splendidly colored spe- 

 cies, the sexes differ so much that they were at first thought 

 to be specifically distinct."' Mr. E. B. Sharpe, who has es- 

 pecially studied this group, has shown me some American 

 species (Ceryle) in which the breast of the male is belted 

 with black. Again, in Oarcineutes, the difference between 

 the sexes is conspicuous: in the male the, upper surface is 

 dull blue banded "with black, the lower surface being partly 

 fawn-colored, and there is much red about the head ; in the 

 female the upper surface is reddish brown banded with 

 black, and the lower surface white with black markings. 

 It is an interesting fact, as showing how the same peculiar 

 style of sexual coloring often characterizes allied forms, that 

 in three species of Dacelo the male differs from the female 

 only in the tail being dull blue banded with black, while 

 that of the female is brown with blackish bars; so that 



" See his "Monograph of the Trogonidse," first edition. 

 " Namely, Cyanaloyon. Gould's "Handbook to the Birds of Australia," 

 vol. i p. 133 ; see, also, pp. 130, 136. 



