254 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
of the color. It is remarkable that in this stage the male and female 
wings are quite similar in general appearance, except that the ground 
color of the male is now a dusky gray, while that of the female is a 
cinnamon-brown. 
From this time onward, however, the wings of the two sexes begin 
to differ more and more in appearance, for the ground color of the 
male becomes deep black, while that of the female remains cinnamon- 
brown. This change is well exhibited by Figs. 3*2 and 39, Plate 3 , 
which give the appearance of the upper surfaces of the male and 
female wings respectively at about twenty hours after the first appear¬ 
ance of the colors. Fig.-33 represents the hind wing of the same male 
whose fore wing is shown in Fig. 32. Figs. 34, 35, 40, and 41 give 
the appearance of the pupal wings just before emergence, when 
the colors are completely formed. 
To summarize; Figs. 27, 29, 33, and 35 give successive stages in 
the development of color in the male ; and Figs. 28, 36-41 give 
similar stages for the female. It becomes evident, from a comparison 
of these successive developmental stages, that the colors appear first 
upon the central portions of the wings, and that the outer and costal 
edges of the wings and the nervures are the last parts to acquire 
the mature coloration. 
It is worthy of remark that the color-pattern of the mature male 
Callosamia promethea is quite a departure from the type of coloration 
which is commonly found among the Saturnidae. The female , 
however, conforms very well to the general pattern of the other 
species of the family. It is quite evident that the deep black colora¬ 
tion of the male is, phylogenetically speaking, a new acquisition, and 
that the coloration of the female represents the less differentiated 
and therefore, more primitive type. 
It is interesting in connection with these facts to observe that the 
color-patterns of both male and female develop in almost identical 
ways up to the twelfth hour after the first appearance of the color ; 
that then, however, the grayish ground color of the male wings 
begins to deepen into the characteristic jet black of the adult, while 
the light cinnamon ground color of the female merely becomes 
slightly darker as the wings mature. 
(3) Development of Color in the Pupal Wings of Danais 
plexippus. Figs. 42-45, Plate 3 , are intended to illustrate four 
stages in the development of color in the pupal fore wings of Danais 
plexippus. The pupal stage of this species is of brief duration, last- 
