THE YOUNG NATURALIST. 



127 



peaty mosses of Lancashire ; owing to vegetation in the Shetland Isles being 

 of a more scanty natnre the pupse are probably more exposed to the action of 

 the sun. Look for instance at Satyrus Janira, of which white and light 

 brown varieties frequently occur in the north of England, caused more or 

 less by the action of the sun on the pupae, shortly before the emergence of 

 the imago. Of those species which are double-brooded, the spring brood is 

 generally the larger and darker. The genus Selenia is a good illustration of 

 this, as well as the female of Lyccena Argiolus. 

 Glanville Wootton, Sherbum, Dorset. 



To be continued. 



BRITISH BUTTERFLIES, THEIR DECREASE 

 AND ITS CAUSES. 



By FRANK G. PRESCOTT DECIE. 



In the March number of the Young Naturalist for the present year is an 

 extremely interesting article by Mr. J. E. Eobson, entitled " Are Butterflies 

 disappearing from the British Isles ?" With most of the statements made 

 j in that article I quite agree, but I cannot, on the present evidence, admit 

 ! the correctness of the two main conclusions to which Mr. Eobson comes in 

 the course of it; without modifications, in the one case slight, but in the other 

 considerable. It is with no small amount of diffidence that I venture to 

 express an opinion adverse to that of Mr. Eobson on such a subject, for 

 my own entomological experiences extend over only a very few years, and I 

 must, moreover plead guilty to being unacquainted with the larvae of so 

 common a species as the Meadow Brown. My hope, however, is that I 

 may by what I am now writing, induce Mr. Eobson, at some future time to 

 bring to the knowledge of the readers of the Young Naturalist some more of 

 the data which assist him in arriving at these conclusions. 



In the first place, then, Mr. Eobson would have us believe that "unless 

 our climate changes, and it is not likely to do so in any perceptible degree, 

 we may expect the British Butterflies to become fewer and fewer in number, 

 and perhaps eventually to disappear altogether, and, that the time is not very 

 far distant, when a large portion of our butterflies will have ceased to exist 

 as natives, and the collector of that day may only expect to fill his series by 

 the chance occurrence of immigrants, or from foreign examples." In arriving 

 at this conclusion Mr. Eobson seems to start from the following premises 



