464 



40. Chironomus dimorphus, n. sp. 



Male. — Thorax greenish yellow, abdomen black. Head yellow; 

 scape of antennae yellow, flagellum and plumes fuscous ; palpi reddish 

 or brownish. Mesonotum opac|ue, the disc slightly pruinescent ; vittse 

 reddish or reddish brown; postnotum blackish brown, paler at base. 

 Abdomen fuscous, shining ; anterior lateral angles of segments usually 

 with an elongate longitudinal yellow streak. Legs pale straw-colored, 

 last tarsal joint generally brownish. Wings clear, veins yellow, cross 

 vein unclouded. Halteres yellow. 



Frontal tubercles indistinguishable ; antennae about one and a half 

 times as long as head and thorax together ; pronotum linear on upper 

 half. Hypopygium as in Figures ii, 12, Plate XXXIV. Legs long 

 and slender; fore tarsi without long hairs, basal joint about one fifth 

 longer than fore tibiae (60:50) ; mid and hind legs with moderately 

 long hairs; basal joint of hind tarsi a fourth shorter than hind tibiae 

 and less than tv/ice as long as second joint (65, 52, 30). Wings 

 slender, third and fourth veins ending at equal distances from apex 

 of wing; cubitus forking almost directly below cross vein. 



Female. — Fuscous or black. Head dull yellow; antennae pale 

 yellow, apical joint and palpi brownish. Thorax with slight whitish 

 pruinescence between vitta% opaque black except on vitta;, which are 

 slightly shining; scutellum black. Abdomen black, shining, poste- 

 rior margins of segments sometimes narrowly yellow. Legs yellow. 



Differs from the male in having the wings broader and in the 

 usual sexual characters. 



Length, 6-7 mm. 



Type locality, Carbondale, 111., April 23, 1914, taken on bank of 

 Crab Orchard Creek (C. A. Hart and J. R. Malloch) ; paratypes 

 taken by the same collectors in the following Illinois localities : Du- 

 bois, Monticello, and Muncie on dates in April, May, and June, the 

 latest date being for the specimen taken at Monticello. A single 

 paratype from Plummer's Island, Md., August, 1907, is in the col- 

 lection of the U. S. Bureau of Biological Survey (W. L. McAfee). 

 It is labeled (by Coquillett) "? jucundus Walker," but Walker's de- 

 scription, though very brief, obviously can not apply to the present 

 species. 



I have examined a large number of specimens of this species 

 taken by A. C. Burrill at Madison, Wisconsin, June, 1912. Many 

 of the males bear labels to the effect that they were taken from 

 swarms flying at 7 : 45 and 7 : 50 p. m. 



This is probably the species identified as albistria Walker by Jo- 

 hannsen. As Walker's description of legs does not agree with that 



