14 
that they have undergone have to be registered by the naturalist of 
to-day. For more than a quarter of a century I have been studying 
more or less continuously our American WVoctutde, and have been 
engaged in resolving by comparison the palzearctic element into 
groups, and showing the existing affinities with the same element in 
the European fauna.* From the mass of species which the student 
readily recognises as distinct arise a small number, the specific 
distinctness of which from the European is more or less difficult to 
establish, and a still smaller number of which we can positively state 
that they offer no distinction whatever. The smaller number offering 
few and varying differential characters are what we call “ representative 
species,” and it is of these that I here chiefly write, referring to a 
paper upon them read before the German Association at its meeting 
in Bremen in 1890. 
No comparison between American and European species is com- 
plete unless all the stages—egg, larva, and moth—are included in 
the comparison, and hitherto few have been so compared. I have 
only done this in one instance. I could find no difference in any 
stage between Luplexia lucipara bred in eastern North America and 
inGermany. I give here a corrected list of the identical species now 
existing in America and Europe. The fact that some Lepidoptera 
have been imported by commerce, such as Porthetria dispar, Zeusera 
pyrina, and perhaps Sesta tipuliformis, together with the white 
cabbage butterfly (the history of the introduction of which has been 
narrated by Mr. S. H. Scudder), as also the introduction of certain 
species of Coleoptera and Diptera, does not seem to apply to the 
case of our identical owlet moths. There is no record of such 
introduction. ‘The habits of the species, the fact that Luplexia 
lucipara is disseminated over the whole country from New York to 
San Francisco, that Scodoptervx Libatrix is found from Hudson’s Bay 
to Virginia seem to preclude the theory of introduction. Again, 
another fact slides in, and this is the most important fact for the 
student to remember. ‘The identical species grade insensibly by 
small shades of difference into the class of ‘‘ representative” species, 
just as these latter do into the great mass of species readily separable 
by the usual specific characters. ‘The theory of unchanged survival 
since the glacial epoch in the case of these identical species is, 
therefore, supported by the evidence. Beyond a few Alpine forms of 
Anarta, the identical species so far more or less fully compared, 
but with present certainty to be assumed, are—Agvots prasina, Fabr. ; 
Agrotis speciosa, Hibn.; Agrotis ypstlon, Rott.; Agrotts occulta, L. ; 
Agrotis saucta, Hubn.; We octua baia, Fabr. ; N octua c-nigrum, 1. ; 
Noctua fennica, T.; Noctua plecta, L.; Enargia paleacea, Esp. ; 
Scoltopteryx libatrix, L.; Heliothis armiger, Hubn.; Aelothis 
scutosus, Fabr.; Mamestra trifolit, Rott.; Xvlophasta lateritia, Hfn. ; 
Flillia crasts, H.S.; Dipterygia scabriuscula, lL. ; Luplexia lucipara, 
* See my paper, “On Allied Species of Noctuidz inhabiting ae and 
North America,” Bull. Buff. Soc. Nat. Sci., October, 1874. 
