INTRODUCTION. XVU 



not found in Europe, H. scutosus and dipsaceus, the latter with a yellow- 

 winged variety, apparently the equivalent of the European maritima, 

 Pyrrhia umbra. Besides these, several species occur in North America, 

 the identity of which with certain European forms is a matter of 

 present uncertainty. We may enumerate the North American Hadena 

 vultuosa, which may turn out to be identical with the European rurea, 

 Caradrina miranda, which may be lepigone-, C. civica, which may be 

 quadripuncta ; Lithophane pexata, which may be ingrica ; Calocampa 

 nupera, which may be vetusta ; Lithomia germana, which may be solida- 

 ginis ; Calpe canadensis, which may be capucina ; Arsilonche henrici, which 

 may be albovenosa. From this it will be seen, that the percentage of 

 identical forms may be considered small, since the North American 

 fauna is sufficiently well known as to prevent the idea that any large 

 additions will be made in the future to the above list. The identical 

 species, when finally fully compared and ascertained, will form a 

 distinct and limited class by themselves. A less distinctly defined 

 class of North American species, are those grouped as "representative." 

 These grade through different distinguishing features, into the large 

 class of perfectly differing species, still retaining the European facies, 

 and then again into the generically peculiar forms only known as yet from 

 North America, but with probably Asiatic and even African allies. 

 There remains then a residue of structural forms peculiar to North 

 America, together with those which intrude into the North American 

 fauna from tropical America, and which, in part, are yearly immigrants 

 over a large portion of the United States and Canada. 



The characters by which the North American representative 

 species are separated from their European allies are unequal in value, 

 taken from different stages of the insect, and are often so slight that, 

 did the European and American form occur together, there would be 

 no question of their specific identity. The fact that these forms do not 

 interbreed, that they do not produce each other, must be taken as the 

 warrant for the assumption of a different specific title. Among the 

 butterflies we have an instance in Chrysophanus phlceas and the C. 

 americana of D'Urban, or hypophlceas of Boisduval. Instances of 

 representative species occur also in the higher Heterocera, but we have 

 to do here especially with their occurrence in the Owlet Moths. The 

 least evident, but at the same time the best-marked character by which 

 European and North American representative species may be distin- 

 guished, is the structure of the male genitalia. We may take as 

 instances of this, the European Agrotis augur and the American A. 

 haruspica, the European Agrotis rubi and the American A. rubifera. 

 The peculiarities of size, form, external structure, colour, pattern of 

 ornamentation of the European augur are reproduced in haruspica. 

 The most that can be said of the moths is, that the American examples 

 tend to an obsolescence of certain markings, and there may be a differ- 

 ence in the exact shade of colour ; probably the latter, with the former 

 character, will not hold good throughout extensive series. Yet the 

 male genitalia show a difference in the details of their shape. The 

 character may not be sufficiently founded, but what is published upon 

 it may be accepted as evidence of the fact. Now there are, in North 

 America, apparently co-existing genitalic species among the Skippers 

 belonging to the genus Nisoniades. The question comes up : are modi- 

 fications of the genitalia of specific value ? That they are not to be 



