176 PROCEEDINGS OF THE ACADEMY OF [Jan., 



therefore much nearer to the tint of the orange ground-color of the 

 rest of the wing. The transition here does not appear to be effected 

 by a gradually increasing number of deep orange scales, but by a 

 rgradual increase in the depth of the tint. The two marks at the 

 end of the cell are nearly as rich an orange as in the expanse be- 

 low t^ie cell, and the transition towards yellow is, on the upper 

 :surface as compared with the lower, shifted towards the costal 

 margin, occurring in the two spots of the same series placed above 

 the end of the cell in areas 10 and 11. The linear spot in area 11 is 

 yellow with thinly scattered orange scales, which are far more thickly 

 placed on the spot in area 10. 



7. The Colored Pigments of the Pierin^ as Illustrated by 



Neophasia. 



Professor F. Gowland Hopkins has shown (11, 13) that the white 

 pigment of Pierines is an impure uric acid, and that the yellow 

 •orange and probably the red pigments are a derivative of uric acid 

 which he calls "lepidotic acid. " No pigments of similar constitution 

 were found in any other butterflies. Therefore, when a Pierine 

 mimics an Ithomiinc or, as in N. terlooti, a Danaine, the resemblance 

 is effected by the production of an entirely different coloring matter. 

 •Gowland Hopkins believes that the yellow, orange, and red Pierine 

 pigments are chemically nearly allied and may pass one into the other 

 by slight changes perhaps in the degree of oxidation. He observed 

 that one tint was represented by another in corresponding markings 

 ■of opposite sexes or allied species. Thus he remarks (13, p. 678) : 



"It is interesting to note, by comparing various allied species of 

 Delias, that the red marginal spot may become more yellow, while 

 ihe yellow area usually found at the root of the wing may become 

 more red, till both may exhil^it a uniform orange colour, or the 

 ■change may go farther and red and yellow change places without 

 the general color-plan of the wing being altered." 



These conclusions are strongly supported by a careful study of 

 Neophasia, where it has been shown that in different individuals of 

 the same sex of menapia the same markings may be either orange, 

 orange-red, or pale vermilion, while in the opposite sex they may be 

 absent or feebly represented in dull orange or yellow. Again in the 

 allied terlooti the corresponding markings are a rich deep vermilion 

 in both sexes. We are led to realize that it is very easy for Neophasia 

 to produce any shade between a pale lemon-yellow and a rich ver- 

 milion. The colored markings of menapia cannot be regarded as 



