FLIES OF GENUS RIVELLIA — NAMBA 49 



pruinose. Laterotergite completely and densely pruinose. Proster- 

 num dark brown or black. 



Thoracic appendages: F'ront legs: Coxae, femora, and tibiae yellow; 

 tarsi blackened from fourth segment, remaining segments yellow. 

 Middle legs: Coxae with brown spot on outside at base; femora and 

 tibiae yellow; tarsi with fifth segment blackened, remaining segments 

 yellow. Hind legs: Coxae and femora yellow; tibiae vary from brown- 

 ish yellov/ to almost black; tarsi slightly blackened from fourth seg- 

 ment, remaining segments yellow. 



Wing (fig. I0,i) length 2.4-3.4 mm. Bands black. First and 

 second bands widely separated at costal margin; third and fourth 

 bands joined at costal margin. Second band definitely obhque to 

 costal margin. The part of first basal cell contiguous to second basal 

 cell entirely hyaline or at most faintly banded basall}^ Section of 

 fourth vein proximad of anterior crossvein with shght bend. Halteres 

 yellomsh brown or dark brown. 



Abdomen: Tergites shining, rugose, brown or black. Disc of first 

 tergite with pale setae. Genitaha (fig. I0,k,l) with apical part of 

 aedeagus wedge-shaped, the two terminal tubes little longer than the 

 base of apical part. 



Females: Body length 3.0-5.1 mm.; wing length 2.4-3.2 mm. 

 Ovipositor sheath concolorous with abdomen. Otherwise similar to 

 males. 



Specimens examined: District of Columbia (299): Rock Creek; 

 June 15. Georgia (19): Atlanta; June 8. Illinois (499, 86" cT): 

 Algonquin; no date. Indiana (399): La Fayette; July 3-12. Iowa 

 (1999, lOd^ cf ): Ames, County 3, County 64, County 76, Des Moines, 

 Ledges State Park, Palisades-Kepler State Park, Sioux City; May 

 25-July 31. Kansas (19): Douglas County; June. Maryland 

 (499): Cabin John Br.; June 14-28. Michigan (299, Ic^): Ionia 

 County, Monroe; July 4-12. Minnesota (5299, 29d'cf): St. Paul 

 Water Works (Anoka County), Gray Cloud Island, Hammond, 

 Mississippi Bluff one-half mile north of state line (Houston County), 

 Owatonna, St. Anthony Park (Ramsey County), Sucker Lake, 

 University Farm, Winona County; June 1-Aug. 3. Missouri (19): 

 Shrewsburry (?); Aug. 6. Nebraska (19): No data. New Jersey 

 (299): Trenton; July 6. New York (999, TcfcT): East Aurora, 

 Flatbush, Irving, Ithaca, Lancaster, Rome; May 27-Aug. 19. 

 North Carolina (299): Valley of Black Mountains; July 10. Ohio 

 (499, Id"): Summit County; July 29-Aug. 11. Pennsylvania 

 (1599, 7 d^ c/") : Delaware County, Kempton, Manayunk, Philadelphia, 

 Swarthmore; May 21-Aug. 13. Rhode Island (1 cT) : Westerly; June 

 29. South Dakota (IcT): Brookings; no date. Tennessee (19): 

 Clarksville; July 4. Virginia (399) : Great Falls, Rosslyn; June 3-25. 



