52 



DIPTERA OF NORTH AMERICA. 



[PART IV. 



of their organization, 

 ing two columns : — 



This contrast is expressed in the follow- 



Limnobina. 

 Epistoma longer than broad. 



Flabs of labium linear, narrow. 



Antennae 14-jointed. 



One submarginal cell. 



Auxiliary vein often short, its tip 

 being then anterior to the inner end 

 of the submarginal cell. 



The great cross-vein is almost 

 always at the inner end of the discal 

 cell, or before it. 



Four posterior cells. 



Tibiae without spurs at the tip. 



Ungues dentate on the under side. 



Empodia indistinct or none. 



A horny, elongated, immovable 

 style on the under side of the 

 forceps, in the male. 



Upper valves of the ovipositor 

 often very short (especially in the 

 genus Dicranomyia). 



Limnophilina. 



Epistoma generally transverse 

 (broader than long) . 



Flabs of labium broad and fleshy. 



Antennae 16-jointed. 



Two submarginal cells. 



Auxiliary vein generally long, its 

 tip being almost always nearly oppo- 

 site the inner end of the submarginal 

 cell. 



The great cross-vein is very often 

 opposite the middle of the discal 

 cell. 



Five (seldom four) posterior cells. 



Tibiae with spurs. 



Ungues smooth. 



Empodia distinct. 



No horny, immovable style on the 

 under side of the forceps. 



Upper valves of the ovipositor 

 generally long. 



The teeth on the under side of the ungues of the Limnobina 

 seem to be peculiar to this section. They must not be confounded 

 with the more or less square or sharp projection on the under side 

 at the very basis of the ungues, forming a part of the thickening 

 which always exists there. The tooth of the Limnobina, even 

 when single, is distinct from this thickening, and placed before it 

 (outside of the Limnobina, Antocha is the only genus which 

 seems to have something like this tooth). The style on the under 

 side of the male forceps is also peculiar to this group ; I have 

 observed something analogous to it only among the Tip. anomalx 

 (Dicranoptycha, Antocha). 



The North American and European Limnobina, as far as 

 known, may be divided in two natural groups, one of which has, 

 in most cases, a short auxiliary vein, the marginal cross-vein 

 always at the very tip of the first longitudinal vein, and the male 

 forceps formed of two fleshy lobes {Dicranomyia, Bhipidia, 

 Geranomyia) ; the other group has, with rare exceptions, a long 



