152 thf; entomologist. 



White proposes the name of Delamerennis, occurs in the 

 " black district" of Staffordshire — in Burnt Wood — not far 

 from which an immense quantity of smoke is produced by 

 the manufacture of iron and pottery. 



When 1 read my paper on " Melanism " before the 

 Lancashire and Cheshire Entomological Society, 1 was 

 under the impression that both Dr. White and Mr. Birchall 

 wished to teach us that natural selection, or the survival of 

 the fittest, was the cause of Melanism. It now appears I 

 was either mistaken or else Dr. White has come round to 

 my views, for, after telling us what natural selection does for 

 Lepidoptera, he asks the question, "What is the exciting 

 cause?" This is just the point. I admit that when a variety 

 has been produced — no matter by what means — it becomes 

 hereditary. If circumstances favour the reproduction of the 

 variety, it may be intensified generation after generation ; or, 

 if it appears under unfavourable circumstances, it may revert 

 to the type form in a ievf generations — but this is all that 

 natural selection has to do with Melanism. I suggested two 

 causes which I imagine are at work in producing dark 

 varieties, and quite agree with Mr. Prest that we must look 

 further. 



When I mentioned these I was well aware that it was 

 only an attempt on my part to account for the dark varieties 

 in two or three species, and 1 know to my great pleasure and 

 wonder that there are extraordinary dark varieties produced 

 in Scotland, These cannot have been caused by smoke or 

 chemicals, but they are, as far as m}^ experience goes, pro- 

 duced in black bog or peat soil, which I suppose contains a 

 large amount of carbon ; and this may have the same effect 

 on the caterpillars, through the tissues of the food-plants 

 containing more carbon than in other situations, as when the 

 caterpillars eat the carbon in the form of soot along with 

 their food. I was at school at York, and have been thei*e 

 since. That city is, I think, as " the crow flies," not more 

 than thirty-miles from Leeds,' the blackest town in York- 

 shire. Why, one can hardly distinguish a white sheep from 

 a black one near Leeds, owing to the quantity of soot that 

 falls on the pasture. Smoke from the district around Leeds 

 will be carried by the wind at least sixty miles ; and if Mr. 

 Prest will put on a pair of while trowsers and walk through a 



