473 



arated; labial plate as in tcntans? (PI. XXIX, Fig. 9) ; ventral blood- 

 gills on eleventh segment, very long, four in number. 



Pupa. — Length, 7-8 mm. Reddish. Frontal tubercles large (PI. 

 XXXI, Fig. 12). Thoracic respiratory organs white, consisting of 

 numerous hairlike filaments. Abdominal segments with the dorsum 

 covered with minute set?e except on lateral and anterior margins and 

 on the apical half of the median line, the setae on apical two segments 

 indistinct ; lateral apical process of eighth segment as in Figure 3, 

 Plate XXXI. 



Imago ; Male. — Greenish yellow, subopaque. Head yellow, antenna? 

 fuscous, scape and base of flagellum sometimes yellowish, plumes 

 bicolored, brown at base and on a space before apex, on the interven- 

 ing space and on apex yellow ; palpi fuscous. Mesonotum with whit- 

 ish pruinescence, most distinct between vittse, the vittae reddish ; lower 

 half of sternopleura, a patch below wing-base, and postnotum reddish. 

 Abdomen green or greenish yellow, each segment with a narrow trans- 

 verse median brown band which rarely extends to the anterior margin. 

 Legs yellow, apices of tibiae and of tarsal joints narrowly brownish. 

 Wings clear, veins yellow, cross vein infuscated; posterior branch of 

 cubitus slightly infuscated. 



Frontal tubercles of moderate size. Hypopygium as in Figure 11, 

 Plate XXXIII. Fore tarsi bare, basal joint distinctly more than one 

 half longer than fore tibiae (80: 52) ; mid and hind legs with long 

 hairs. Venation as in serus. 



Female. — Agrees with the male in color except that the abdominal 

 bands are generally broader and extend closer to the anterior margins 

 of the segments. 



Length, 5.5-7 mm. 



Illinois localities : Illinois River for a considerable distance north 

 and south of Havana; Urbana, St. Joseph, Dubois, and Mt. Carmel, 

 on various dates in the months of April, May, June, September, and 

 October. This species often occurs at light. The larvae occur almost 

 as commonly in the Illinois River as do those of viridicollis. They 

 also occur almost everywhere in streams and ponds, and commonly 

 pass through the pipes conveying the household water-supply in cities 

 where the reservoirs are unprotected, as mentioned under znridicollis, 

 the appearance of the "blood-worms" often causing unnecessary 

 alarm. Probably the commonest species of the genus. 



Originally described by Johannsen from material representing the 

 following states : New York, Ohio, Illinois, Iowa, Kansas, Washing- 

 ton, and Nebraska. 



