42 NEW-WORLD MIMICS [ch. 



selves are already transparent there would appear 

 to be no reason why this should be so. Of course 

 the process has not proceeded in all of the forms 

 to the same extent. There is least change in Ituna 

 where the scales are not much reduced in size and 

 where a fair proportion are still pigmented. There 

 is probably most in an Ithomiine such as Thyridia, 

 where the scales are not only small and entirely without 

 pigment, but also are for the most part neckless so 

 that they stand out at right angles to the wing. Having 

 regard to the fact that several widely separate genera 

 with different types of scaling formed the starting 

 points, the final results do not seem to preclude the 

 supposition that the transparency has arisen through 

 a similar process in all of them. 



It is somewhat remarkable that no Satyrine exhibits 

 mimicry in S. America, in spite of the fact that trans- 

 parency of the wings, as in so many of the butterflies 

 of this region, is quite common in the group. On 

 the other hand the relatively large number of more 

 or less mimetic Pierines is a striking feature of S. 

 America. For the most part they belong to the 

 genera Dismorphia and Perrhybris, and resemble the 

 yeUow, black, and brown Heliconines and Ithomiines, 

 though some of the former genus are mimics of the 

 small transparent Ithomiines. Some of the species 

 of Pereute with their dark ground colour and the 

 bright red bar across the fore \ving (PI. XI, fig. 6) 

 resemble Heliconius melpomene, as also does Papilio 

 euterpinus. But some of the most interesting Pierine 



