1924 ] Concerning the Availability of Taxonomic Characters 169 
found, but which has disappeared in many Tachinidse. These 
hairs are found in some Stratiomyidae, Syrphus s. s., Bomby- 
liomyia of the Tachinidae, and several Calliphorid genera. Here 
again we have a character of doubtful value taxonomically, but 
one which might be considered to indicate relationship, and at 
the same time one which may be used to great advantage in 
the treatment of several genera. 
It should be remembered that there are many characters 
not of true generic or family significance which are nevertheless 
of the greatest importance as aids in determination, and it 
seems advisable in very many cases to treat these as of generic 
importance merely for our convenience. If, by the use of such 
characters, we split up several genera, placing many of their 
representatives in a single genus, and eliminate other supposed 
genera, we are simplifying the determination of many species; 
it is surely advisable to use such a character. If our classifica- 
tion is such that genera are of but little assistance in the deter- 
mination of species, or are not truly separable from each other, 
it is evident that we need a change in methods: — either that, or 
the elimination of genera entirely and the use of family names in 
a generic sense. A superabundance of genera is almost an 
equivalent of the foregoing condition. Perhaps the best ex- 
ample of this latter condition is to be found in the Tachinidse 
where more than one thousand genera have been proposed, and 
at least half that number are recognized. It is not likely that 
more than one hundred genera should be recognized in this 
family if we are to have a classification of the maximum assis- 
tance in determination of the species. Characters being in- 
vestigated at present indicate that several genera in the Tachi- 
nidse and Dexiidse can be lumped together to great advantage, or 
at any rate isolated into very distinct and easily recognized groups. 
The above information is submitted in the hope that work 
along the lines indicated may be stimulated. There is much to 
be done but one must proceed carefully in dealing with a subject 
of this nature, taking pains not to overemphasize the value of 
such characters as have been enumerated, and to investigate as 
fully as possible before recording results. 
