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ON THE SCENT-PATCHES OF THE PTERINS. 

 By F. A. DiXEY, Oxford. 



It is well known that the males of many species of Pierine 

 butterflies are furnished with an apparatus for distributing 

 the characteristic odour, which is generally of an agreeable 

 nature, belonging to that sex. This apparatus usually takes 

 the form of specialised scales, which may be either scattered 

 broadcast over the wings, or collected into more or less definite 

 patches. In the former case the scales are as a rule of the kind 

 known as " plume-scales," being provided at the distal ex- 

 tremity with a tuft or fringe of delicate chitinous tubules which 

 appear to be pervious, and so to allow the escape of the volatile 

 substance, probably of an oily nature, which carries the per- 

 fume. In the latter case, though the scales may sometimes 

 be of the plume-bearing kind, it more often happens that they 

 are without the plume-like appendage, though they show other 

 evident marks of specialisation when compared with the ordinary 

 scales of the wing. Plume-scales are almost invariably con- 

 fined to the upper surface of the wings ; scent-scales of the 

 other kind may be found on either the upper or lower surface, 

 in many cases on both. 



In several species of the genus Disnioyphia the scent-scales 

 of each wing are collected into an oval patch, usually quite 

 conspicuous, which is situated on the lower surface of the fore- 

 wing and the upper surface of the hindwing. These patches 

 are so placed that in the ordinary position of rest the forewing 

 patch is superimposed upon the patch of the hindwing, and 

 the escape of the odour from both is presumably thereby pre- 

 vented. During flight, both patches present a free surface to 

 the atmosphere, and no apparent obstacle exists to the dis- 

 persal of the perfume. In Dismorphia (Acmepteron) nemesis 

 each oval patch is surrounded by a smooth, shining area with 

 a silky or pearly lustre, the oval patch itself having a roughened 

 or " chalky " appearance. These differences are due partly 



