42 Colouration in Animals and Plants. 



spots, there being as much white as black in the tip, Fig. 5, Plate IV. 

 In A. belia, Fig. 6, Plate IV, the black tip is more developed, and in 

 the variety simplonia still more so, Fig. 7, Plate IV. We here see 

 pretty clearly that this dark tip has been developed by the confluence 

 of irregular spots. 



Turning now to the discoidal spot we shall observe a similar 

 development. Thus in : 



A. cardamines, male, it is small and perfect. 



Do. female, larger ., 



A. belemia large 



A, belia large with white centre. 



Do. v. simplonia small and perfect. 



*A. eupheno, female, nearly perfect. 



Do. male, a band. 



We here find two distinct types of variation. In A. belia we 

 have a tendency to form an ocellus, and in A. eupheno the spot of 

 the female is expanded into a band in the male. 



The orange flush again offers us a similar case ; and with regard 

 to this colour we may remark that it seems to be itself a develop- 

 ment from the white ground-colour of the family in the direction of 

 the red end of the spectrum. Thus in the Black-veined white 

 (Aporia cratcegi) we have both the upper and under surfaces of the 

 typical cream-white, for there is no pure white in the family. In the 

 true whites the under surface of the hind-wings is lemon-yellow, in 

 the female of A. eupheno the ground of the upper surface is faint 

 lemon-yellow, and in the male this colour is well-developed. The 

 rich orange, confined to a spot in G. rhamni becomes a flush in G. 

 Cleopatra, and a vivid tip in A. cardamines. These changes are all 

 developments from the cream white, and may be imitated accurately 

 by adding more and more red to the primitive yellow, as the artist 

 actually did in drawing the plate. 



In A. cardamines the orange flush has overflowed the discoidal 

 spot, as it were, in the male, and is absent in the female. But in 

 A. eupheno we have an intermediate state, for as the figures show, in 

 the female, Fig. 8, the orange tip only extends half-way to the 

 discoidal spot, and in the male it reaches it. Moreover it is to be 

 noticed that the flow of colour, to continue the simile, is unchecked 

 by the spot in cardamines, but where the spot has expanded to a bar in 



* See Plate IV. 



