224 CALIFORNIA ACADEMY OF SCIENCES. 



age between the adult male and female. The general 

 color is brown like the adult female instead of black 

 like the male, but the characteristic rose-colored patches 

 of the adult male on the under wing coverts are fully 

 developed in the young, and the patch of rose on the 

 breast is present, but much interrupted. The young 

 female is almost like the adult, but the yellow paler and 

 colors less pronounced. This species exhibits four stages 

 of evolutionary progress, and it is possible to trace the 

 phylogeny of the adult male from the plain brown 

 streaked bird with pale salmon-yellow under wing coverts 

 (young female) to the more pronounced pattern of the 

 adult, although still obscured by streaks, and with the 

 yellow of the wing coverts more strongly developed 

 (adult female), through the stage in which the yellow 

 patch, by the action of sexual selection in intensifying 

 the correlative color becomes changed into rose, and an 

 irregular patch of the same is developed on the breast 

 (young male), until finally the black, white and rose 

 plumage, in well defined patches, is assumed by the 

 adult male. 



The last class (10) which, however, has already been 

 encroached upon, includes those species in which the 

 adult male is more conspicuously colored than the adult 

 female, and the young male unlike the adults of either 

 sex, but the young female generally like the adult. The 

 best examples of this class with which I am familiar are 

 to be found among the woodpeckers, especially Dryo- 

 bates and Xenopicus. Here the general color and 

 markings do not vary much with age or sex, but the 

 head markings are very peculiar. The red head mark- 

 ings of the adult male are upon the nape, those of the 

 young male cover the top of the head, being, in fact, 

 not only differently located, but more extensive. The 

 head of the female is unmarked with red in the adult. 



