270 BRITISH LEPIDOPTERA. 



Hein.. " Wien. Monats.." 1862, p. 303 ; Hein. and Sta., " Zool.," 1863, p. 83G9 ; 

 Nolck., "Lep. Fn. Estland," p. 773 (1871); Staud. and Wocke, "Cat.," p. 337 

 (1871) ; Hein. and Wocke, Schmett. Deutsch.," p. 748 (1877) ; Sand, " Cat. Lep. 

 Auv.,"p. 201 (1879); Wallgrn., ' Ent. Tids.," ii., p. 127 (1881); Bang-Haas, 

 " N. H. Tids.," xiii., p. 217 (1881) ; Peyer., Cat. Lep. Als.," 2nd Ed., ii., p. 104 

 (1882) ; Snellen, " De Vlinders," etc., p. 991 (1882) ; Sorhagen, " Die Kleinschmett. 

 Brandbg.," p 306 (1886) ; Hering, " Stett. Ent. Zeit.," lii., p. 220 (1891) ; Meyr., 

 " Handbook," etc.. p. 720 (1895). 



ORIGINAL DESCRIPTION. Alls anticis fusco-aeneis, apice purpureo- 

 tincto, fascia postica argenteo albida ; capillis luteis, f usco-mixtis. 

 Exp. al. 2 lin. Head and face yellowish, slightly mixed with fuscous ; 

 antennae fuscous, basal joint whitish. Anterior wings bronzy-brown, 

 considerably beyond the middle is a silvery-whitish fascia, of variable 

 breadth, placed nearly perpendicularly ; the apical portion of the wing 

 is purplish-brown ; cilia fuscous. .^ Posterior wings grey, with grey 

 cilia (Stainton, Ent. Annual, 1856,'p. 42). 



IMAGO. Head ochreous. Anterior wings 5 mm. ; bronzy-brown, 

 the tip purplish-brown ; considerably beyond the middle of the wing 

 a whitish fascia, nearly straight ; cilia purple-grey tipped with whitish 

 grey, at the anal angle darker. Posterior wings and cilia grey. 



SEXUAL DIMORPHISM. The males are rather smaller and browner ; 

 frequently the fascia does not extend quite to the costa, and the head 

 is fuscous, with white eye-caps. The females are purplish from the 

 base to the fascia, which extends quite to the costa, and the head is 

 yellow. The insect varies in intensity of colour with the temperature 

 and climatic conditions of the season. Some years ago, in a hot 

 summer, I bred some as brilliant as N. alnctdla (Threlfall). In the 

 male, the frontal tuft is pale luteous-yellow, sometimes almost dirty- 

 white, the small cervical tuft still paler, the eye-caps small and silvery- 

 white ; in the female, the frontal tuft is bright ochreous-yellow, the 

 cervical tuft luteous, the larger eye-caps are pale yellow with a 

 silvery gloss (Heinemann). 



VARIATION. The moths that I bred in September, 1894, from larvre 

 feeding in leaves of Betula nana, and sent to me from Rannoch, by 

 Salvage, may be this species, but they are smaller, have black heads in 

 both sexes, and the fascia is distinctly more silvery and less golden, and 

 the apical cilia have more whitish scales, especially near the costa, than 

 those bred from B. alba, and obtained in Tilgate Forest and Abbott's 

 Wood. I am by no means convinced that the northern insect is 

 identical with our southern N. betulicola (Fletcher). 



COMPARISON OF N. BETULICOLA WITH N. MICROTHERIKLLA, N. PLAGI- 

 COLELLA, ETC. The fascia of N. betulicola is more posteriorly placed 

 than in .V. Hiirnttheriella, in the latter, too, the fascia is not shining ; 

 in N. betulicola it is perceptibly silvery (Stainton). This species is 

 most nearly allied to N. jilar/icolella, and is sometimes very difficult to 

 distinguish from it, but the latter has the frontal tuft much brighter 

 ferruginous, and the antennae are longer, reaching in the female to 

 the middle of the anterior wings, and in the male perceptibly beyond 

 the middle ; besides, in N. playicolella, the ground colour of the 

 anterior wings is more bronzy, paler and more glossy, and not so 

 inclined to black-grey ; before the fascia there is a more decided 

 violet tinge ; the base, on the other hand, is always rather paler, dull 

 bronze-colour; the fascia is, just beyond the middle of the wing, 

 rarely as narrow as in N, betulicola, and has a more decided metallic 



