Color and Pattern and their Uses 
597 
completely formed and merely lack pigment. In about forty-eight hours 
after this (see Fig. 784, a) the ground-color of the wings changes to a dirty 
yellow. It is interesting to note that the white spots which adorn the mature 
wings remain pure white. Fig. 784, b, illustrates the next stage, where the 
black has begun to appear in the region beyond the cell. The nervures 
Fig. 785.—Diagrammatic series showing development of color-pattern in pupal wings 
of the promethea moth, Callosamia promethea; female wings in vertical series at left, 
male at right. (After Mayer; one-half natural size.) 
themselves, however, remain white. Fig. 784, c, shows a still later condition, 
where the dirty yellow ground-color has deepened into rufous, and the black 
has deepened and increased in area and has also begun to appear along the 
edges of the nervures. In Fig. 784, d, the black has finally suffused the 
nervures, the base of the wing and the submedian nervure being the only 
