STEFCTUEE AND LITEEATUEE. 27 



the oneliand, tlie upper surfaces of the hind wings 

 tend to resemble the lower surfaces of the primaries : 

 they are dull, unhanded except by one or two ex- 

 terior cloudy lines. In position these moths hold 

 the primaries over the secondaries, shielding the 

 upper surface of the latter from the light and air 

 during the daytime. It is as if the pattern of the 

 one was photographed upon the other. In the other 

 direction, the ornamentation tends to be uniform on 

 the upper and under surfaces of both pair of wings. 

 Tlie transverse lines run across both wings, so that 

 the upper surfaces of the primaries and secondaries 

 come to look alike. In this case the moths rest in 

 the daytime with the hind wings more or less ex- 

 posed and after the fashion of the Geometridae. In 

 comparing the method of variation, I have found 

 that in the Noctuidre, especially those belonging to 

 the first group, or Xoufasciatce, representative forms 

 differ first, and most strongly, in the appearance of 

 the upper surface of the primaries, then in the 

 secondaries, and lastly in the under surface of the 

 wings. Thus the American Catocala Relicta, which 

 belongs to one of the higher genera among the 

 FasciatcB, approacliing the NonfasciatcB in the posi- 

 tion of the wings at rest, and which represents the 

 European C. Fraxbii, difl'ers more or less noticeably 

 by the fore wing above. On the hind wing the 

 dusky blue band of the European species becomes 

 white in the American; while I have previously 

 shown that, in some specimens, there is a narrow 

 blue edging retained in C. Bellcta, throwing light on 

 the origin of the species (Can. Ent. viii. 231). In 



