196 DIPTERA OP NORTH AMERICA. [PART IV. 



marks, besides the two infuscated cross-veins (humeral and super- 

 numerary) ; a large spot is situated at the basis of the wing, 

 between the first longitudinal vein and the posterior margin ; its 

 anterior part is tawny, the remainder brown ; a brown band 

 begins at the posterior margin, before the tip of the seventh 

 longitudinal vein; it extends to the fourth vein, where it assumes 

 a tawny color and emits two branches ; the posterior branch is 

 connected with the two angular marks in the costal cell ; the 

 anterior branch expands into a large brown spot, occupying a 

 considerable portion of the marginal cell and emitting a branch 

 which runs along the central cross-veins, as far as the fifth vein ; 

 the apical portion of the wing contains a band, running across 

 from the tip of the second longitudinal vein to the tips of the 

 fifth and sixth veins ; this band emits a branch towards the apex 

 of the wing. All these bands are very irregular, and they vary 

 in extent in different specimens ; those of the apical portion of 

 the wing are surrounded with irregular dots, streaks, etc. 



Eab. Washington, D. C, in July and August. A Brazilian 

 specimen in the Berlin Museum seems to belong to this species. 



Gen. XXVIII. LIM^ T OPIIII,A. 



Two submarginal cells ; usually five, seldom four posterior cells ; discal 

 cell closed ; subcostal cross-vein posterior* to the origin of the second 

 longitudinal vein, usually closely approximated to the tip of the auxiliary 

 vein. Wings glabrous. Eyes glabrous. Antennse 16-jointed. Tibiae with 

 spurs at the tip ; empodia distinct ; ungues smooth. 



The diversity of forms, comprised under this definition of 

 Limnophila, has already been alluded to above (p. 190). I have 

 not been able to introduce a satisfactory natural arrangement, 

 partly on account of the difficulty of the task, partly owing to the 

 limited materials at my disposal, especially with regard to the 

 European fauna. Epiphragma and UlomorpJia, two small, but 

 apparently well circumscribed genera, I have separated from 

 Limnophila ; but it would be premature, 1 think, to do the same 

 with some of the other subdivisions, adopted by me in 1859. 

 Some American species, discovered by me since, do not exactly 

 answer the definitions of those subdivisions, as I understood them 

 at that time ; often, the relationship is evident, but difficult to 

 define in a satisfactory manner. The present genus is therefore 

 left in an unfinished condition. 



