50 THE ENTOMOLOGIST. 



I was at once struck by the approximation of these figures to 

 Mendelian proportions for simple opposed characters. 



I did not obtain any wild larvcie in 1914, so could not repeat 

 the experiment until the next year, when af^ain a couple of very 

 darii local type forms were selected. Unfortunately, the larvae 

 hibernated badly, and only 19 survived to emerge in June, 1916. 

 These were as follows : 13 type forms ranging from light to 

 dark, 4 var. rohsoiii, and 2 dark plunibosa. In this instance the 

 small proportion, about 6 per cent., of imagines does not confirm 

 the assumption of Mendelian inheritance, although the fact that 

 all the three variations again appeared from similar parentage 

 suggests that segregation of two opposed characters does occur. 



What is perhaps more remarkable, however, is the sudden 

 appearance of the black form robsoni as a distinct aberration. 

 So far as I am aware, the black varieties of nebidosa have never 

 before been bred from any form of the type, when both parents 

 have been of the grey-mottled character, but, on the other hand, 

 they always appear if one or both parents are black; hence, 

 robsoni would be expected from a wild type female if she had 

 paired with a black male. 



I do not wish in this article to expand the suggestiveness of 

 this result in its bearing upon the general origin of melanism, 

 but as it arises from the two experiments it should not be passed 

 over without mention ; it will suffice to remark that probably we 

 have here an indication as to the genesis of the black forms 

 Q'obsoni and thompsoni of nebidosa. 



The variation I now propose to call plambosa is bred annually 

 from wild larvae to the extent of 1 to 3 per cent., hence, next to 

 thompsoni it is the rarest of the naturally occurring forms ; it 

 also varies from leaden-grey to fuscous-grey in ground-colour, 

 but is never black, in this respect being parallel to the lighter 

 and darker forms of the local type. 



The following is a description of var. plunibosa : Fore-wings 

 leaden-grey to fuscous-grey ; stigmata faintly outlined with 

 ■white and exteriorly with black ; transverse lines faintly white, 

 posteriorly black, interruiDted ; a transverse series of small black 

 acute tooth-shaped marks representing the subterminal line ; on 

 the termen a series of black lunules and dots; the veins in the 

 subterminal region black ; hind-wings, in both sexes, uniform 

 •dark grey, the veins darker than the ground-colour. Head, 

 thorax, petagia, and abdomen as in the local type (var. bimacu- 

 iosa, Esp.), but slightly darker. Types, two males and two 

 females, representing palest and darkest, in coll. W.M. 



4, Norwich Road, Liverpool, 

 January 27th, 1917. 



