SEXUAL DIVERSITY IN BUTTERFLIES. 873 



of the front wings ; but occasionally it is very marked, as in many of the 

 hair streaks, where the branches of the subcostal vein near the end of the 

 cell are thrown far out of place to accommodate a patch of j)cculiar 

 crowded scales. This patch itself, moreover, is a feature of the males 

 alone, and occurs in many hair streaks where the position of the vein is 

 not altered. 



One of the most curious patches of this kind is found in the males of 

 certain yellow butterflies, of the genus Eurymus, although wholly absent 

 from others intimately allied to them ; it is a little patch of lustreless 

 scales which occurs at that part of the base of the hind wings which is 

 always covered by the front wings, so that it is quite concealed ft-om sight. 



Patches of a different nature also mark the male sex ; thus next the 

 middle of the lower median vein of the hind wings of Anosia plexippus 

 and in some of its allies, we have a thickening and inversion of the mem- 

 brane, forming a little pocket and conspicuous from its covering of black 

 scales. 



In certain swallow tails, as in our Laertias philenor, the inner border 

 of the hind wings of the male is folded back upon itself, concealing some 

 pure white floss-like scales and hairs, which are apparently exposed at the 

 will of the creature, when it is moving forward in flight. 



Then, again, there is much variety of male adorment in special modifi- 

 cations of hairs or scales ujion the wings ; the patch of the hair streaks, 

 just mentioned, is one instance of this ; another example is found among 

 the fritillaries in a row of long, fulvous, partially erect hairs along the 

 upper edge of the cell of the hind wings ; this is accompanied by a curious 

 apparent thickening of the veins in the middle of the fore wing, due al- 

 together to the presence of a multitude of small and densely clustered 

 black scales crowded against the veins at this point. A faint oblique 

 patch of minute and crowded lustreless scales, accompanied by long silky 

 hairs, is often seen crossing the wings of some of the satyrs or meadow- 

 browns ; and if we were to go for our examples outside the range of our 

 own species, these examples might be multiplied indefinitely. 



Sexual dimorphism shows itself in the legs in the proj^ortional length of 

 the different pairs in the two sexes, in the special development of certain 

 joints, in the appendages, and in the clothing. It appears remarkably in 

 the appendages of the two higher families of butterflies, Nymphalidae and 

 Lycaenidae, and especially in the latter family, where the terminal appen- 

 dages of the fore legs are nearly or quite lost in the males, and are as 

 conspicuous as on the other legs in the female. I have not discovered 

 that the differences in the length of the leg-joints follow any general law, 

 although there are few of our butterflies whose sexes do not vary in this 

 particular ; this form of antigeny is also most conspicuous in tlic Lycaenidae. 

 The males of certain Chrysophanidi (Chrysophanus, Epidemia, Ileodes, 



