( c ) 



common type. But tliis is not invariably the case ; it some- 

 times happens that the plume-scales are conspicuously shorter 

 than the other scales amidst which they are embedded. 



Having now briefly discussed the usual appearance aud 

 chai-acteristic features of these structures, I propose in the 

 next place to give some account of the various forms assumed 

 by them in the different Pierine genera ; noting incidentally 

 any mai-ked exceptions to the general statements advanced 

 above. For the sake of uniformity I employ the generic names 

 adopted by Dr. Butler in his arrangement of the Pierinae in 

 the National Collection ; these having also been used by me in 

 a paper on Pierine Phylogeny in our " Transactions " of 1894. 

 A few of his identifications have been altered in accordance 

 with the present arrangement in the British Museum. 



The Indian and Malayan genus Ixias consists of white 

 or yellow butterflies with an orange tip which may be 

 absent in the female. All the species are provided with 

 plume-scales, which with one exception bear a strong family 

 likeness to one another. The exception is Ixias marianne, 

 one of the white species, in which the lamina is sharply 

 triangular. In the other forms of Ixias the lamina is rather 

 long and narrow, slightly compressed laterally, and somewhat 

 expanded at the base, which tends to be bilobed. Ixias nola, 

 the other white species, has a plume-scale which bears a greater 

 resemblance to the yellow forms than to I. marianne, though it 

 approaches the latter in the sharpness of its apex. In all the 

 species the disc is moderate in size, oval or circular. 



The large orange-tipped butterflies belonging to the genus 

 Ilebomoia are furnished with plume scales which are not 

 unlike those of Ixias, though much larger. The lamina is 

 long, narrow, and laterally compressed, with an acute apex 

 and rounded base. The footstalk shows a sharp curve ; the 

 disc, moderate in size, is often depressed in the middle, thus 

 becoming concavo-convex or ladle-shaped. The appearances 

 presented by the fimbriae are a little difficult to interpret. 

 Some of them seem to be bifid, especially those towards the 

 base of the apical triangle. Frequently they appear to end in 

 sharp-pointed hooks, which on a change of focus are i-eplaced 

 by well-defined circular dots giving the idea of terminal 



