142 THE VALUE OF COLOUR 



man while the apparently aposematic scents in 

 both sexes of species with warning colours should 

 be displeasing to him. But the former is far 

 more surprising than the latter. It is not per- 

 haps astonishing that a scent which is ex hypothesi 

 unpleasant to an insect-eating Vertebrate should 

 be displeasing to the human sense ; but it is 

 certainly wonderful that an odour which is ex 

 hypothesi agreeable to a female butterfly should 

 also be agreeable to man. 



Entirely new light upon the seasonal appear- 

 ance of epigamic characters is shed by the recent 

 researches of C. W. Beebe, 1 who caused the 

 scarlet tanager (Piranga erythromelas) and the 

 bobolink (Dolichonyx oryzivorus) to retain their 

 breeding plumage through the whole year by 

 means of fattening food, dim illumination and 

 reduced activity. Gradual restoration to the 

 light and the addition of meal-worms to the diet 

 invariably brought back the spring song, even 

 in the middle of winter. A sudden alteration 

 of temperature, either higher or lower, caused 

 the birds nearly to stop feeding, and one tanager 

 lost weight rapidly and in two weeks moulted 

 into the olive-green winter plumage. After a 

 year, and at the beginning of the normal breeding 

 season, ' individual tanagers and bobolinks were 

 gradually brought under normal conditions and 

 activities,' and in every case moulted from nuptial 

 plumage to nuptial plumage. ' The dull colors of 



1 The American Naturalist, xlii. No. 493, Jan. 1908, 34. 



