Maurice T. James

An Objective Aid in Determining Generic Limits

THE present paper does not attempt to define a genus; it deals with the methodology rather than the philosophy of systematics. The genus, however, is here considered as a natural grouping of species, a branch of the phylogenetic tree. As such, its members have in common a number of fundamental characters, morphological and otherwise. The genus, therefore, is to be defined on the basis of the totality of characters, not on key characters which, though often fundamentally important, are primarily of utilitarian value. The method proposed here, one which I have used successfully, may avoid the creation of useless new generic names or concepts, many of which are proposed simply because they are based on forms which do not fit into existing keys. The method is not wholly original; Forbes (1934) used a similar plan in determining relationships between genera of the agrotine moths. The application to the differences existing within rather than among