224 Journal New York Entomological Society. [Vol. xxi. 



legs. The hypopygium is enlarged only near Tethina, and the ovi- 

 positor is specialized rarely outside of the Agromyzinae, where it is' 

 cuneiform or tubular. However, the number of abdominal segments 

 is not constant, and should be observed. 



In describing genera these preceding characters should be mainly 

 noted. Meigen, Zetterstedt, Schiner and Loew lived before the days 

 of chsetotaxy and their descriptions are hard to interpret into the fol- 

 lowing tables. These tables have been constructed from what speci- 

 mens I have had to study, and I am not answerable for the correct 

 assignment of those genera I know only from descriptions. However, 

 my collection of this group includes thirty-seven genera, one hundred 

 and sixty-five species and about two thousand specimens, mainly, of 

 course, North American, and without such a representation this work 

 would have been impossible. The lack of definite information in the 

 older descriptions concerning characters now considered important 

 has made it necessary at times to select characters that we would not 

 willingly stress. The identification tables are thus largely artificial ; 

 some of the groups seem natural and phyletically related, but often 

 the association of genera and species in the tables is due to the arbi- 

 trary emphasis of some selected character. All the genera hitherto 

 known, the world over, are included in the tables of genera, but only 

 the species known to occur in North America are given in the tables 

 of species. In presenting them I trust that the tables will be work- 

 able, and that they will help and not hinder other students in unravel- 

 ing the intricate species of this little known group. 



The nearest relatives of the species herein discussed are the Dro- 

 sophilinse, Oscininse and Ephydrinse. In fact, the Geomyzinse are 

 more nearly related to the Drosophilinae than they are to the Agro- 

 myzinje. Acarthrophthalmiis of the Heteroneurinse closely resembles 

 the Agromyzinse, but its auxiliary vein is more distinct and separate 

 from the first vein and the break in the costa is near the humeral 

 crossvein. 



The accompanying tabulation of characters is given for the prin- 

 cipal groups with which the species discussed herein might be con- 

 fused. In explanation, the sclerites comprising the cheeks, the lower 

 occiput, gena, bucca and center of the face are abbreviated O, G, B 

 and F, respectively, and the most important one is mentioned first. 

 Where there is but one costal break it occurs near the end of the 



