MosLEY : On Causes producing Variety in Lepidoptera. 53 



shares with the golden and spotted eagles the peculiarity of being 

 the only British members of the family FalconidcB that are feathered 

 to the foot, I should be inclined, were I competent to be a systematist, 

 to place the genus Buteo next to that of Pandion, that is before the 

 true falcons, the hawks, and the kites, which now intervene. But I 

 rest quite content in knowing that those worthy of being looked up 

 to as authorities have ordained otherwise, and I accept their decisions . 

 Leeds, October 20th. 



ON SOME CAUSES WHICH SEEM TO OPERATE IN THE 

 PRODUCTION OF VARIETIES IN LEPIDOPTERA* 



By S. L. Mosley. 



Now that I have examined almost every large collection of lepidoptera 

 in England, for the express purpose of picking out those which differ 

 more or less from the normal type, it may not be out of place if I 

 throw out a hint or two as to some of the causes which seem to 

 me to operate in the production of these varieties. The subject 

 is as yet very obscure, and we require a great deal of facts and 

 data before we can attempt to form any theory as to the uses or 

 purposes of these variations. Some of them may seem clear and 

 certain both as to their use and the cause or causes which produced 

 the variation, but we have yet a great deal to learn ; and it is only 

 by each one telling what he knows — and only what he knows — that 

 we can hope to arrive at any definite or satisfactory solution of the 

 problem. 



Some species of lepidoptera seem very constant, and we scarcely 

 ever find anything differing from a given standard line in colour, or 

 arrangement of pattern on the wings. "Who, for instance, ever saw 

 a var. of any of the Sesidcs except the white-belted culiciformis ? — 

 always the same transparent wings, and bodies belted with either red 

 or yellow ; or of any of the genus Procris ? — always the same uniform 

 brassy green ; or of any of the Litlioddce ? Of course slight varieties 

 have now and then occurred even in these, but as a general rule they 

 are very constant, and anything approaching to a variety is very rare. 

 A great many of the Noctuce^ too, seem remarkably constant in their 

 characters ; others, on the contrary, seem to have an almost ever- 

 lasting change of colour or pattern : and I might give as instances 

 two favourites of the variety -breeder, Ohelonia caja and Abraxas grossu- 



* Eead before Huddersfield Scientific Club, Oct. lOth, 1879. 



