}00 Descrijitions of New JSFoctuaz, etc. 



XXVIII. — Descriptions of J¥eiO Noctum, with remarks on 

 the variation of Larval Forms in the Group. 



Br A. R. GROTE. 

 Read Dec. 11th, 1876. 



I have already called attention in the "Popular Science 

 ^Monthly" (for December, 1876), to the method of variation 

 displayed by certain kinds of JYbctuce. These variations were 

 observed in the cases of representative species, that is to say 

 forms which have an ally in a widely separated locality, such 

 as Europe is when compared with our Atlantic Coast Territory. 

 It was found that the differences between such species are ex- 

 pressed on the upper surface of the wings (especially the 

 front pair) most prominently; the under surfaces in the con- 

 trasted forms agreeing very nearly in both color and design. 

 An instance was cited in the North American Catocala relicta 

 and the European Catocala frapcini. Although the differ- 

 ences between the two are greater than in some other cases, 

 and the changes' undergone by one form or the other, or both, 

 since a separation from a common stock, are thus greater 

 than has often happened, yet the peculiar color and size of 

 the two insects render the comprehension of the fact more 

 easy. Beneath, both species have remained white. Above, 

 the European form contrasts by its more uniformly gray and 

 obscure primaries ; in the American insect, these are white, 

 more or less invaded by transverse bands of more intense 

 gray or black. It is suggested that the habit of the moths 

 which ensures the concealment from light, and from the 

 more immediate atmospheric changes, of the under surface 

 of the body and wings, has been the principal factor in the 

 case. In the day-time, the moths rest against an opaque 

 substance, the fore wings covering the hind pair. Both these 

 species belong to the subgenus Catocala, as limited by 

 Hubner. They are structurally identical ; and no other 

 species of this particular subgenus of the large genus Catocala 



