( xoix ) 



on the ground that scales of many diverse forms covild be 

 found in the same individual. This, of course, is perfectly 

 true ; nevertheless the suggestion is not entirely unworthy 

 of notice. There are probably few cases, if any, where a 

 specific diagnosis can be made from the ordinary wing-scales. 

 But it is occasionally possible on an inspection of these 

 structures to pronounce with some confidence on the genus 

 of their possessor. The long spatulate scales of the genus 

 Pinacojiteryx, for example, can scarcely be mistaken, and the 

 short, rounded scales of Baltia and Pliulia are characteristic. 



When, however, the plume-scales ai-e examined, the case is 

 seen to be entirely different. These, speaking generally, are 

 fairly constant within the limits of a species, and often present 

 distinct specific features. Still more striking are the characters 

 exhibited by them which may be called generic. Though 

 there are some remarkable exceptions, it would on the whole 

 be true to say that most of the genera now usually recognised 

 could be defined on the structure of their plume-scales ; a cir- 

 cumstance which is satisfactory as tending to show that our 

 Pierine genera are for the most part natural groups. No one 

 who had once seen the plume-scale of any African species of 

 Mylotliris could ever take it for anything else, nor could he 

 fail to recognise the genus of any other African Mylotliris 

 whose plume-scale he might meet with afterwards. In this 

 connection it is interesting to observe that the plume-scales of 

 the American species pyrrlia, mcdenka, lypera, and lorena are 

 of an entirely diiferent type from the African species with 

 which they have been supposed to be congeneric. This is so 

 far confirmatory of the opinion expressed by me many years 

 ago, in agreement with Mr. Trimen, that the aflSnities of these 

 American species must be sought in another direction ; any 

 resemblance between them and the African Mylothris being 

 merely superficial. I shall have more to say on this point 

 presently. 



There is sometimes a kind of rough relation between the 

 ordinary scales and the plume-scales in the matter of size. The 

 ordinary scales differ much in dimensions, particularly in 

 length, between different species. Elongated plume-scales are 

 frequently found in relation with elongated scales of the 



G 2 



