are no such species in the f/n.i'm-group, makes it probable that the 

 former is of older derivation than the latter, and the excessively- 

 unstable condition of the species of this group in Europe, where it 

 seems to have specially developed itself, which might be held to 

 militate against this view, does not really do so, since this condition 

 is more than matched by the Asiatic species which cluster round 

 didijma, and for range of variation there is no species — not even 

 excepting athalia — which can even approach another member of the 

 cm.i'trt-group, namely, plicehe. Of the athalia-gxow]) the most primi- 

 tive member is certainly aster ia, and though this species has so far 

 been found only in the Alps and the Altai, yet it is so extremely 

 local that it maj^ easily yet be found in other high ranges, or on the 

 other hand the same causes which so restrict its habitats would be 

 likely also to lead to its extinction. The other high mountain 

 species, which in Europe stands alone, raria, is in Asia the centre 

 of a small group, asteroidea, solona, and more distantly halhita, all of 

 which however show distinct cinxiid affinities on the underside, and 

 constitute one of the special puzzles of this genus. I have dealt at 

 such length on a previous occasion with the European species of the 

 athalia -gxoxx^, that I must not now enter at all fully into this branch 

 of the subject, and must content myself with referring to my paper 

 in the "Entomologist," especially the June, August, and October 

 numbers for 1910 for the reasons which still compel me to believe 

 in the specific value of britoniartis and dictijnnoides, and to reject the 

 extravagant claims which have been made as to the importance of 

 the genitalia as a final court of appeal as to the identity or other- 

 wise of nearly related species. 



This latter question, however, seems to me so important that I 

 cannot refrain from quoting a few paragraphs of the observations I 

 then made on the subject, though they must be read in eu-tenso to 

 give more than a superficial idea of the matter. Amongst other 

 remarks I wrote as follows : — " Of course, if the differences were 

 such as to debar insects from pairing, no claim based upon them for 

 the differentiation of species could possibly be regarded as extrava- 

 gant, for the circumstance would of necessity act automatically in 

 keeping species apart ; and I readily admit that there was a time 

 when I was a full believer in this ' lock and key ' theory, as it has 

 been called, and was under the impression that only the most closely 

 connected species would ever pair in a wild state, and that the fact 

 of insects of different species ever pairing (except in captivity) was 

 in itself enough to show that they were at least congeneric. It is 

 now of course a matter of common knowledge that scarcely any 

 pairing, even in a wild state, is out of the question, unless some 

 obvious reason should render it physically impossible ; and it would 

 be a mere matter of searching in periodicals and the ' Zoological 

 Record ' if one wished to produce a long list of what would other- 

 wise be astounding cases. Here are a few picked up at random in 

 the course of searching for information on a widely different sub- 



