8G [September, 



closely engaged in other work, and living, moreover, in a district in vrhich there was 

 little opportunity of studying either form, the matter was deferred ; and recently 

 it has been taken up by others, and some very interesting papers on the subject have 

 been published, but I still think that a little remains to be said. 



As I understand it, the alleged distinction between the two species or forms 

 consists in two points: — The ground colour, which in crepuscularia is brownish, in 

 biundularia whitish ; and the time of appearance, which in crejntscularia is from 

 February to April, according to the season, in biundularia May and June. A third 

 point has been put forward, the double broodedness of crepuscularia as distinguished 

 from the other, which is said to bo single-brooded ; but this is a mistake. I have 

 taken second brood specimens of both forms in July or August, in the south of 

 Surrey, and have them now before me. It can hardly be necessary to point out that 

 this is with very many species a mere question of latitude, species being single 

 brooded in the noi'th, or even in the midlands, which are double, or partially double 

 brooded in the south of England. 



As we have these forms in the south then, crepuscularia — emerging generally in 

 March or April — has the ground colour whitish, almost entirely obscured by lighter 

 or darker brown dots, or by a brownish clouding towards the costal and hinder 

 margins. The first line faintly indicated, brown, and accentuated generally by three 

 black spots situated on ncrvures. Second line brown, with a black spot at every 

 nervure, those in the middle being the most distinct. This line has a duplicate in 

 lighter brown just beyond it, and in this, opposite the two large central spots, is a 

 somewhat square, dark brown, blotch, sometimes conspicuous. Between the first 

 and second lines is a faint brown central shade, darker at the costa, and having two 

 black dots in the middle. Before the hind margin is a third line, broken and dis- 

 connected, and having generally two dark brown or black spots above the middle. 

 This line has also its duplicate nearer the margin, and there is a black dot in the 

 space between the terminations of the nervures at the base of the cilia which are 

 spotted with brown. Specimens are by no means uniform, but vary in the degree of 

 intensity of all the brown markings, and to some extent in the number of black 

 spots. 



Biundularia — emerging in the south, generally in May — may be described in 

 precisely the same terms, except that the brown scales are very much fewer, and all 

 the brown markings paler, so that the black spots are more noticeable, but it is quite 

 impossible lo find any reliable mark constituting a distinction between them. Every 

 spot, shade, line, and blotch is placed precisely in the same position and proportion, 

 and, under a lens of low power, even the dusting of bi'own scales differs in nothing 

 but degree. 



In the hill districts of the midland and northern counties we come upon quite 

 a different sot of forms, but all, or nearly all, seem to agree in this one respect, that 

 tlie tinge of warm fulvous-brown has disappeared, and is replaced by umber, or, 

 more frequently, by various shades of grey, and in very many the grey becomes so 

 dark as to obscure or even efface nearly all the normal markings. In this last case, 

 however, a narrow space between two of the hindermost dark bands remains pale or 

 even whitish, constituting a character never observable in the normal forms. These 

 more northern specimens are generally a little smaller than those from the south, 



