Mimetic Relationships in the genus Heliconius. 103 



change in texture. In Section II there is, adjacent to the 

 median and its branch, a certain amount of dull " meali- 

 ness." This amount may be very small, but it is always 

 recognisable, especially after a very little practice. The 

 two sections were designated by the extremely clumsy 

 names of Opisogymni and Opisorhypari respectively. 

 For convenience they mav be referred to as Section I 

 and Section II. Between these two sections the reputed 

 species are nearly equally divided. In the monograph 

 referred to Section I contains 31 species and 110 sub- 

 species, whilst Section II includes 39 species and 79 sub- 

 species. This division is apparently a natural one, and 

 so far as my preparations go the genital armature of no 

 species of Section I could be mistaken for that of a species 

 of Section II. 



Section I may now be further divided, and we will first 

 consider the forms included by Riffarth under the name 

 Silvaniformes. These include nearly all those species 

 the patterns of which are composed of yellow, brown, 

 white, and black markings. Generally speaking, it may 

 be said that the ground-colour of one or both wings is 

 brown or yellow, though there are one or two exceptions. 



The evidence of the genitalia. 



Whilst the genitalia of nearly all the members of this 

 group are readily distinguishable from those of the rest 

 of the genus, they are by no means so readily separable 

 inter se. Moreover, at least one form hitherto regarded as 

 rather widely separated from the Silvaniformes must now 

 be included in that group. I refer to H. atthis. In the 

 accompanying plates the genitalia have been illustrated 

 by giving "a carefullv drawn outline of one clasper, as it is 

 from the^shape of this part that any conclusions can best 

 be drawn.* After examination of a large number of pre- 

 parations, it appears that they may be divided more or less 

 into those which have a dense hairy 1 uft near the end ol 

 the clasper and those which are only moderately pilose. 

 Whether this feature is of real value or not is difficult to 

 decide; if, however, we accept the feature it would seem 



* I much regret the poor quality of these plates. The presenl 

 necessity for economy has. however, made H impossible to use the 

 beautiful lithographic process by which the figures were reproduced 



in my paper on Acraea. 



