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 dislally and then each branch splits 



Fig. 778. — Scales taken from a single fore wing of Megalopyge crispala, 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 arisonesis, 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 fonning wing of a 

 butterfly during the pupal or chrysalid stage confirms the hj-jjothesis 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- 



