18TG.) 



i;3i 



niohuiic varieties in Scotland is caused by the existence of iron in the 

 soil in large quantities, by tlie excessive moisture of the climate, or by 

 the absence of sunshine ; as a matter of fact, I do not know that there 

 are any Lirge deposits of iron ore in the Highlands, and even supposing 

 any or all of the suggested explanations to be coincident with the 

 existence of melanism, it is still needful to show their connexion with 

 it as cause and effect, which has not been attempted. 



It must further be noted, that melanic varieties of Leindoptera 

 occur very commonly in Ireland, the Isle of Man, Durham, South 

 Lancashire, and the West Eiding of Yorkshire, under various con- 

 ditions of climate and soil. 



Near Leeds, Aplecta nehulosa and Xylophasia 2)oh/odon are often 

 perfectly black, and the "black pepper" {Biston hetidaria) is as well 

 known in the woods as its namesake is in the store-room. 



Near Manchester, the melanic variety of Biston hetidaria has 

 become very common of late years, and threatens to supplant the 

 typical form. I quote the following from a note in Newman's 

 " Entomologist," vol. ii, p. 150, by the late R. S. Edelston :— " Some 

 "sixteen years ago, the ' Negro ' aberration of this common species 

 " was almost unknown. Last year, I obtained the eggs of a female of 

 " the common form, which had been crossed with a ' Negro ' male ; 

 " the larvae I fed on willow, and had this year some remarkably pretty 

 "aberrations, the connecting link between the ' Negro ' and the usual 

 " form, but far before either as regards beauty. I placed some of the 

 " virgin females in my garden, in order to attract the males, and was 

 " not a little surprised to find that most of the visitors were the 

 " ' Negro ' aberration ; if this goes on for a few years, the original 

 "type of A. hetularia will be extinct in the locality." 



In all the districts I have named, besides the tendency to the 

 production of melanic forms, we may also notice the existence of a 

 very meagre Lepidopterous fauna ; and, although from our ignorance 

 of the conditions which are of most importance to any animal, it is 

 hazardous to try to point out the special circumstances which prevent 

 its spread or check its fertility, perhaps the following may be suggested 

 as not improbably amongst the causes at work in limiting the numbers 

 of Lepidoptera in Scotland, Ireland, the Isle of Man, and the North 

 of England : — The peculiarities of the climate of Ireland, and the Isle 

 of Man being deficient sunshine, excessive moisture, and almost entire 

 absence of frost, it may be suggested that, under such conditions, the 

 hibernation of larvae and the sleep of pupse are incomplete, and 

 that damp and mould make many victims. Over wide districts of 



