250 THE ENTOMOLOGIST. 



parts by an extremely thin wavy line of the pale grey ground colour. 

 Far more numerous are specimens in which the three lines are 

 all distinct, but thinner, and with the outer half of the marginal 

 band either absent or much reduced, and most visible at the 

 nervures. In a considerable number, about one-fifth, of the 

 specimens the second line is absent, except just at the dorsum. 

 The two very pale forms mentioned in the 'Entomologist,' June, 

 1904, may be regarded as an extreme form of this. The first 

 and third lines are very thin, and the second almost entirely 

 obsolete (fig. 1). Both parts of the marginal band are merely 

 represented by a slight deepening of the ground colour. 



With regard to the relative positions of the lines, the first is 

 very regular, varying only slightly in its distance from the base; 

 the second and third are liable to considerable alteration. As a 

 rule they pass on either side of the discal cell, and as they 

 approach the dorsum become united by a group of black scales 

 lying between them. It is not unusual to find this taking place 

 earlier, and causing coalescence just beyond the discal cell. In 

 one specimen the whole space between the two lines from costa to 

 dorsum is filled with black scales, and a black band passes across 

 the centre of the wing. The marginal band in this male is, 

 however, poorly developed (fig. 2). The second and third lines 

 vary in distance from the discal cell. In two specimens the 

 second line passes through this, and in another between it and 

 the termen. The second and third lines are thus more nearly 

 parallel, though remaining quite distinct (fig. 3). 



With regard to the marginal band, its distance from the third 

 line is not regular, and its width must therefore vary correspond- 

 ingly. Of its two halves the outer is more liable to become 

 faint. In fact, in only one have I seen the reverse. In this 

 specimen the inner half gradually fades away as it approaches 

 the costa. In these paler forms the fringes also are lighter. 

 The secondaries show traces of two lines close together at the 

 dorsum, separated by a fine line of ground colour, and there is 

 an additional sign of the outer of these at the discal spot. In 

 a bred male the second or outer of these is visible fairly clearly 

 right across the wing, and the inner can also be traced, though 

 very faint. As in the primaries, they pass on either side of the 

 discal spot, enclosing it between them. 



The ground colour of all my captured specimens is pale cold 

 grey, or, in the specimen described in the June number, dark 

 grey (fig. 4). In my few bred specimens I find that in every case 

 except one it is a clear cream colour, giving a richer appearance, 

 especially to the secondaries. This cannot be due to fading in 

 the wild ones, as they were freshly emerged. Possibly the food 

 of the larva may have some effect, the bred ones feeding on 

 birch, and in one case Calkina vulgaris, and the captured 

 specimens on Erica or Myrica. 



