152 Annals Entomological Society of America [Vol. IV, 



It should be stated that the ultimate categories of genera, 

 or those which will eventually be found most serviceable for 

 taxonomic recognition and which I shall call group units, 

 may be considered as generally equivalent to tribes in other 

 groups of insects. Most of the series given in these addenda 

 are to be considered as such, and for that reason I have given 

 them the names of the genera dissected and studied. 



The article by me in a recent issue of "Science" entitled 

 "On muscoid and especially tachinid synonymy, may be pro- 

 fitably read in connection with this preliminary outline of results- 

 to date in the Muscoidea. 



