Page:Memoirs on the coleoptera (IA memoirsoncoleopt01case).pdf/11

Rh genera which differ among themselves only in sexual modifications at the ventral apex,—though often most important if supplemented by structural differences elsewhere,—on the other hand, is eminently proper. And, after all, what is to be gained by trying to aggregate these structural groups of species under a single name, as in the case of the comprehensive genus Atheta of the most recent school? Not only is there no discernible advantage in this procedure, but we subject ourselves to very great inconvenience in efforts to prevent duplication of specific names in such enormous single genera. This difficulty is also becoming pronounced in Stenus, but there it seems impossible to suggest the relief afforded by generic subdivision, which is so proper in Atheta because of the widely diversified facies as well as structure prevailing in the latter group; in Stenus the facies is very consistent throughout, and most of the subdivisions that have been proposed are apparently not true genera from any reasonable point of view. The European catalogue of Heyden, Reitter and Weise of 1895 is far superior to that of 1906, not only in its more sensible treatment of the Athetæ, as being composed of at least a few admittedly valid genera, but especially because our sense of propriety is not offended by the wholly unnecessary reversal of the usual succession of subfamilies, tribes and genera in the great family Staphylinidæ given in the latest edition of that work.

Another mistake frequently made, and a very serious one, is in assuming that nearly all exotic forms can be forced into the genera of purely European species. Some genera are common to Europe and America, but the isolation of the latter region since the middle Tertiary has sufficed for the evolution of many distinct types, so that at present there are a great many more endemic American genera than of those common to the two continents. The same remark applies as well to the species, the least resemblance between species of the two continents. The same remark applies as well to the species, the least resemblance between species of the two continents sufficing some superficial observers for a verdict of identity, which is false as a rule. There are some species common to America and Europe but not many, and they constitute an exceedingly small proportion of the whole number known; moreover virtually all such are likely to be cosmopolitan.

There have been but few attempts ever made to systematically arrange the genera and subgenera of Athetæ in accordance with their structural differences, and I would here bring forward one