Color and Pattern and their Uses 



593 



hair becomes a scale by shortening and broadening, keeping its free 

 tip entire; in others the hair splits distally and then each branch splits 



\l 



FlG. 778. Scales taken from a single fore wing of Megalopyge crispata, showing grada- 

 tions from true hair to specialized scale. (Greatly magnified.) 



again, and so on, while the base is continually shortening and broadening 

 so that the scale form finally reached is a fingered or deeply-toothed 



FIG. 779. Scales from a single fore wing of Gloveria arizonesis, showing gradations from 

 scale-hair to specialized hair. (Greatly magnified.) 



one. But in all the series the final result is that from a long, slender, sub- 

 cylindrical hair is evolved a short, broad, flattened, little scale. A study 

 of the actual development of an individual scale on the forming wing of a 

 butterfly during the pupal or chrysalid stage confirms the hypothesis of the 

 evolution of the scales. In the growing developing wing the scales begin 

 as hairs, arising by the extension of certain hypodermal cells in the wing- 



