68 



larvae of these insects are, in some respects, not quite identical 

 but the insects themselves are very similar. Again, the 

 variation of pullata, like that of obscuraria, ranges from a 

 white or whitish form on the one hand, to a black or blackish 

 form on the other. 



" Dihicidaria, Hb., has a certain superficial resemblance 

 to the paler form of obscuraria, but on a closer examination 

 the structural differences of the two insects are at once 

 apparent. 



" By way of illustrating the variable character of obscuraria y 

 in the ground colour of its wings more especially, I exhibit 

 specimens from widely distant British localities. The first 

 three are from Folkestone, and these in tone of colour lead 

 up to the darker coloration of the New Forest and Perthshire 

 specimens in the next row. The third and fourth rows are 

 from North Devon and Lewes respectively. 



" From these examples it will be seen that in each locality 

 the species is represented by a different form, and each form 

 seems fairly constant in its particular locality. The Folke- 

 stone, New Forest, and Perthshire specimens are more or less 

 typical. The North Devon examples come near to, but are 

 not quite, Staudinger's var. argillacearia> and the Lewes 

 insects approach the var. calceata, Staud. 



" Mr. Jenner Weir, in an elaborate paper on 'Variations in 

 the colour of Lepidoptera,' ' Entom.' xvi. 169-176, says (p. 

 173), ' as an instance of a topomorphic variety, dependent, ap- 

 parently, on the geological environment, I know of no better 

 example than that of Gnophos obscuraria? With regard to 

 the forms before you this evening it would be difficult to 

 imagine coloration more suitable for each in its peculiar 

 habitat than that which it possesses. 



"In the production of these varied forms there is, I 

 think, no question of food influence. The differences 

 between the darkest and lightest specimens is simply one of 

 more or less blackish pigment, and the amount of such pig- 

 ment is regulated by the laws of natural selection and in- 



