FUNGUS GNATS OF NORTH AMERICA. I3I 



what longer than the abdomen, microscopically setulose, oval, 

 with more or less rounded base ; costa produced far beyond the 

 tip of R4+r,^ but not quite reaching the tip of the wing; subcosta 

 short or long, ending in the costa, or free, or in H^ ; R^ ending 

 ir the costa beyond the middle of the wing; Sco (subcostal 

 crossvein) usually wanting; the small cell (Rj) somewhat elon- 

 gate, beyond the middle of the wing; the R-M crossvein elon- 

 gate, very oblique, almost' longitudinal in position, appearing 

 like the beginning of a longitudinal vein ; petiole of the media 

 moderately long ; cubitus forking either near the base of the 

 wing or somewhat distad of this point ; anal veins vestigial. 

 The larvae have been found in rotten wood and in fungi. 



Table of Species. 

 a. Subcosta ends in the costa ; a fossil species from Colorado. 



I. peritula. 

 aa. Subcosta does not end in the costa ; living species. 



b. Subcosta vestigal, ends free (fig. 85) thorax and 



abdomen shining black. 2. nitida. 



bb. Subcosta ends in R^ nearly midway between humeral 



crossvein and the base of the radial sector. 



c. Abdomen yellow ; cubitus forks near its base. 



N. H. 3. bicolor. 



cc. Abdomen brown, posterior margins of second 



and following segments yellow : cubitus forks 



at a point nearly opposite the proximal end of 



the R-M crossvein. Pa. 4. pimpla. 



I. Tetragon euro peritula Cockerell. 

 1909. peritula, Cockerell. Amer. Jour. Science XXVII, 53. 

 A fossil species from the Florissant. Colorado. 



2. Tctragoneura nitida Adams. 

 1903. nitida, Adams, Kan. Univ. Science Bui. II. 23. 

 Female. Length 2.7 mm. Black, shining; head black, front 

 bearing yellow pile, antennae dark brown, first two joints and 

 palpi yellowish ; mesonotum black, shining, pile yellow, bristles 

 on margins black, scutellum black, bristles yellow, metanotum 

 and pleura black, halteres yellow, abdomen wholly shining 

 black, pile yellow ; legs yellow, with tip of hind femora, middle 

 and hind tibiae and all tarsi brown : wings hyaline, tinged with 

 l)rown on the anterior part, subcosta short, ending free, the 



