501 



Imago; Male. — Brown-black to deep black, slightly shining. Head, 

 including antennal plumes, fuscous. Thorax with gray pruinescence 

 which is particularly distinct between the vitta;, the latter distinctly 

 shining ; scutellum and postnotum subshining, black. Abdomen black, 

 shining, the posterior margins of the segments usually covered with 

 grayish pruinescence. Legs varying in color from brownish yellow 

 to fuscous, the bases of femora, the tibiae, and bases of tarsi generally 

 slightly paler than other portions. Wings slightly grayish, veins pale 

 brown ; Halteres yellowish or pale gray. 



Antennie rather thick and short, flagellum tapering from base to 

 apex, entire antennal length about ec[ual to that of head and thorax 

 together, number of joints 15. Pronotum of moderate breadth, cen- 

 tral excision wide. Hypopygium as in Figure 16, Plate XXXVII. 

 Legs rather stout ; fore tarsi without long hairs, basal joint about nine 

 tenths as long as fore tibiae (47: 52), second joint less than half as 

 long as basal (21 ) ; mid and hind legs with rather short hairs ; all tarsi 

 with well-developed pulvilli and empodia. Cross vein at middle of 

 wing; third vein ending much farther in front of wdng-apex than 

 fourth does behind it ; cubitus forking slightly beyond cross vein, its 

 posterior branch almost straight. 



Female. — Agrees with male in color. 



Differs in having 8-jointed antennae and the mid and hind legs 

 without hairs, their surfaces having only short pubescence. 



Length, 3.5-4.5 mm. 



Type locality, Havana, III, April 28 to May 2, 1914 (C. A. Hart 

 and J. R. Malloch). Paratypes from Momence, 111., July 17, 19 14, at 

 light (C. A. Hart), and from W'ashingon, D .C, August 6, 1907 (W. 

 L. McAfee). 



The species occurred in great numbers on the Illinois River, and 

 specimens were captured at a considerable distance from it, where no 

 suitable breeding places were available, evidently having been carried 

 there by the wind. 



The species is named in honor of Mr. R. E. Richardson, who has 

 been for several years studying the biology of the Illinois River in 

 connection with the work of the State Laboratory. 



Cricotopus Van der Wulp 



This genus as originally defined by \^an der Wulp was a rather 

 arbitrary one, separated as it was from Orthocladiits merely by the 

 color of the legs. In Cricotopus the legs are pale yellow, or whitish, 

 and black, while in Orthocladius thev are unicolorous black or yellow- 

 ish, rarely yellow with brown markings. Occasionally, however, the 



