402 PEKCT SLADEN TEUST EXPEDITION. 



costal area suffused with blackish tof, whence the sufiFusion is sometimes produced down- 

 wards to a small blackish spot lying within and above base of cleft, a similar black spot 

 lies on lower corner of base of cleft, and these two spots sometimes tend to be connected 

 by blackish suffusion, a few scattered blackish scales in disc between J and f ; first 

 segment cut at about f by a narrow transverse white line, not parallel to termen, preceded 

 by a patch of blackish suffusion most evident on costa and sometimes extended inwards 

 along hinder margin to base of cleft ; second segment cut by a transverse white sub- 

 terminal line, parallel to termen, usually preceded by blackish suffusion. Cilia on costa 

 blackish except for a short distance beyond f and before apex, where they are of the 

 ground-colour of wing ; on termen whitish, with a small black scale-tooth at fore angle 

 of second segment and small black teeth slightly before posterior angle of both segments ; 

 within cleft grey-white (pale fuscous in 2 ), blackish-fuscous subterminally ; on dorsum 

 whitish with a slight admixture of blackish, with slight black scale-teeth beyond ^ and 

 at about f and a rather larger pretornal tooth ; cilia arovmd tornus blackish. 



Hind wing cleft from about ^ to J : first segment subspatulate, apex acute, termen 

 oblique, posterior angle well marked ; second segment parallel-sided, apex very acute, 

 termen very oblique and very slightly concave, posterior angle traceable ; third segment 

 sublinear, tornus obsolete: greyish-fuscous in cf , dark fuscous in ?. Cilia greyish 

 in s , dark fuscous in $ ; first two segments with small wisps of darker basal scales at 

 both angles ; on dorsum without any scale-tooth or heavy scales. 



Type ( 6 ) and cotype ( 9 ) in Brit. Mus. 



Twenty-three specimens (14. c? , 9 $ ) from the Seychelles from Mahe (Morne Blanc, 

 800-1000 feet, and Cascade Estate, 100-1000 feet) and from Silhouette (Mount Pot-a-eau, 

 1500 feet, and Mare aux Cochons, 1700 feet). 



The appearance of the two sexual forms is so different that at first I separated up the 

 specimens as belonging to two distinct species. However, beyond colour and a slight 

 difference in size — the dark specimens expanding on the average about 2 mm. more than 

 the light — I can perceive no valid distinction, and as the light specimens are all 6 6, 

 whilst of the dark six are certainly $ $ (the other three have theu- abdomina missing), 

 I think it may be assumed that we have to deal with a single species only. In one case I 

 find a 6 (liglit) and 2 (dark) pinned on to one stage ; these two specimens were both 

 captured on Mount Pot-a-eau (Silhouette) and were possibly taken in copula, though there 

 is no record to that effect. 



It is quite unusual to find sexual dimorphism in the coloration of the wings amongst 

 members of this family *, and I have therefore considered the name dimorpha an especially 

 suitable one. 



In several respects this species resembles a Stenoptilia, but the possession of scale-tufts 

 in dorsal cilia of fore wing (though not in hind wing) appears to place it more naturally 

 amongst the Platyptilice, although it might be placed with almost equal propriety in 

 either genus or in a new genus intermediate between these two. 



Prom other points of view this species is an interesting one, and we may regard it as a 



* In the New Zealand species Stenoptilia charadrias, Mep., the sexes are differently coloured and might readily 

 be taken for distinct species, but, as noted above, such a case is unusual in this family. 



