MELANISM AND MELANOCHROISM. 89 



a generally exposed species, or one that usually rested on the 

 ground, would be of a lighter race ; Gnophos obscurata, Eubolia 

 bipunctata, Anaitis plagiata offer almost parallel cases in Kent. 

 I would here again call attention to the fact that Dr. F, 

 Buchanan White {Ent. Mo. Mag., vol. iv,, p. 248) suggested 

 the absence of wood from Breadalbane, as one of the reasons of 

 the difference between insects from that locality and Rannoch: — 

 " Breadalbane, however, has higher mountains and less wood, 

 which may perhaps account for the difference." 



In Ent. Mo. Mag. xxv., p. 40, Dr. Chapman writes; — " Melan- 

 ism appears to be a western, rather than a northern form of 

 variation ; to be associated with a wet, rather than with a cold 

 climate ; and it has certainly been more common of recent 

 years, which may be attributed to the long succession (unpre- 

 cedented) of wet seasons we have recently passed through. 

 My observation was on D. fagella. Twenty years ago this 

 species afforded here an occasional dark or even black var. 

 Happening to meet with one of these, I searched carefully for 

 two seasons, but only got one black and two dark specimens. 

 For the last year or two (result of wet seasons) they have been 

 fairly numerous. Visiting certain oak trees with a lantern one 

 night, lately, and the same observations might, occasion 

 favouring, no doubt have been made during the day, I found 

 the dark var. quite numerous, and about one to three of the 

 ordinary form." Strange to say, the same thing has happened 

 in this locality, the dark var. of this same species may now be 

 frequently obtained in this district, and the general colour is 

 undoubtedly getting darker ; in fact, last March, I obtained a 

 specimen in Shooter's Hill Woods, near here, as black as the 

 Huddersfield specimens. Many other species, Cnspidia {Acro- 

 nycta) psi for example, are darker in London than a few miles 

 out, and I have little doubt that " natural selection " does this 

 work, considering the general darkening of surface, which 

 objects in London undergo. But the smoke of London has 

 less intensifying force, so to speak, than that of Yorkshire, 

 because the atmosphere is less humid, and hence the melanism 

 of lepidoptera in this district is less general and intense than 

 in localities, where, with an equal quantity of smoke, there is 

 a greater rainfall or more humid atmosphere. 



I have heard many observant and thoughtful lepidopterists 

 attempt to correlate dark forms occurring in woods, etc., such 

 as I have previously referred to, with the deficiency of light in 

 such situations, and attempt to argue that this deficiency acts, 



