TRANSPARENCY IN WINGS OF LEPIDOPTERA. 119 



Heterosais sYLPHis. — The course of development is precisely the 

 same in this Ithomiine, except that the modified Y- or V-shaped hairs 

 are rather longer than in the last species. Where the dark opaque 

 portion oi' the wing merges into the transparent area, the broad scales 

 are seen to be considerably modified, while the long narrow scales are 

 apparently as yet not in any way specialised, pointing to the fact that 

 the broad scales, perhaps, commenced modification earlier than the 

 ■others. 



■■'■■•'■ Stalachtis ph^dusa. — -The means of obtaining transparency in 

 this species is amazing in its complexity. In the normal scaling of 

 the wings there are two superimposed layers ; the underneath layer is 

 composed of broad fan-shaped scales, with several teeth on the upper 

 ■edge, and these lie flat down upon the membrane. A second layer of 

 scales project through and over the first, and these are of elongated 

 shape, and are a good deal set up on edge. In the transparent portions 

 of the wing area the upper scales are all hair-like, while the lower 

 Ibroad scales have become transparent, and, in addition, appear to 

 Tub or wear off pretty easily, while the hair-like scales are very 

 numerous, and do not to any extent wear off, unless it be after pro- 

 longed existence. A mediocre specimen examined did not show more 

 than a few of these hair-like scales removed, but a great number of 

 the transparent underneath scales were missing. On the inner margin 

 of the hindwing there is hardly a trace of the transparent scales, and 

 the portion nearest the apex has most. In the forewing also the 

 iregion of the outer margin is best scaled. 



Stalachtis evelina. — In this species precisely the same pro- 

 cess takes place as in the last, and the transparent scales are 

 evidently very easily rubbed off, as, except in one or two places, 

 hardly any of these are to be seen. On the underside the broad 

 •costal half of the wing, which is black on the upperside, is developing 

 towards transparency, and the major portion of the flat scales have 

 become transparent, there being still some scattered dark scales 

 amongst them. 



Lauron partita. — From the very incomplete transparency of this 

 species one surmises that it has probably developed the tendency later 

 than any other individual of the group. The scales are of two shapes, 

 and are arranged alternately. In the opaque portions of the wings 

 these two scales are long and slender and short and slender respectively, 

 and are pointed rather abruptly at the tip. In the transparent areas 

 both sets of scales have become much narrower, but not hair-like, and 

 are raised slightly above the membrane. Hardly any reduction in 

 numbers, if any, has taken place, and, altogether, the transparency is 

 most incomplete. The small scales, besides their altered shape, have 

 lost some of their pigment, but the larger scales show no development 

 whatever in this direction. 



Hyrmina protecta. — The scales of this species are extremely 

 varied, some are rather long and pointed, others are short and 

 pointed, while some are broad and either dentated or not. In the 

 transparent areas simple bristles are alone visible ; a few are consider- 

 .ably longer than others, but none are bifurcated as in the Ithomiines. 

 There is no reduction in the number of scales. 



It will be seen from these results that the most common and usual 



** A third Stalachtis, viz., cephalena, has since been added to the group. 



