1890] 



THE YOUNG NATURALIST. 



53 



pinivorana. The place where I took it is only a few yards from where 

 I get Nemophora pilella, and it is a rough, trying, uphill journey from 

 any station. 



Ashton-on-Ribble, 19th February, 1890. 



A NOTE ON MELANIC VARIATIONS OF LEPIDOPTERA, 



By C W DALE, F.E.S. 



In the February part of the Young Naturalist, Lord Walsingham, 

 in referring to a paragraph in the Introduction to my History of our 

 British Butterflies, writes — "It has been frequently and conclusively 

 proved by experience that dark surfaces do absorb and radiate heat 

 more rapidly than light surfaces. The simple experiment of placing 

 pieces of black or white paper, or cloth, on snow exposed to the sun, 

 will show that the black melts the snow beneath it, and sinks into it, 

 with more rapidity than the white." Snow is white, but suppose for 

 arguments sake, snow to be black, then we should probably find that 

 white paper or cloth, would melt the snow beneath it, and sink 

 into it with more rapidity than the black. I doubt if Lord Wal- 

 singham would be prepared to carry his theory into practice by looking 

 at an eclipse of the sun, through a white-washed instead of a smoked 

 piece of glass. 



The pith of any argument is this — dark soils absorb a great deal of 

 moisture, and in consequence cannot absorb so much heat as light soils 

 which are dry. Insects as a rule are darker in wet seasons than in dry. 

 Vegetations again is brighter, and shoots forth earlier in the spring 

 time on dry soil than on wet. 



Northern species of Lepidoptera are not necessarily dark. In fact 

 several of the Shetland forms are not so dark as those of the same 

 species further south. I am referring especially to Chortobius typhon, 

 Hepialus hamuli, and Cry modes exults. This I believe is due to a 

 smaller rainfall. 



Lord Wolsingham also writes " Mr. Dale points out that even in 

 " the South of England darker varieties occur in cold wet lands, than 

 "on light dry soils," and adds, " Yes, and for the same reason, namely, 

 "the advantage they derive by rapid absorption of such limited heat as 

 is available," I certainly cannot see the pith of his argument here. 

 Does his Lordship wish to imply that there is less sunshine, and a less 



