FLIES OF GENTJS RIVELLIA — NAMBA 55 



Thoracic appendages: Front Legs: Coxae, femora, and tibiae yel- 

 low; tarsi slightly blackened from second segment or from tip of 

 first segment, remaining segments yellow. Middle legs: Coxae 

 brown; femora and tibiae yellow; tarsi wholly yellow or slightly 

 blackened from fourth segment. Hind legs: Coxae yellowish brown; 

 femora yellow ; tibiae yellow or brown ; tarsi wholly yellow or blackened 

 from third segment. 



Wing (fig. 10,a) length 2.6-3.6 mm. Bands dark brown. First 

 and second bands widely separated at costal margin; third and 

 fom'th bands joined at costal margin, fourth band narrow, about as 

 broad as third band. Second band appears almost perpendicular to 

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

 basal cell wholl}^ banded, with semicux-ular h}' aline spot anterior to 

 apex of second basal cell, or faintly banded at base. Section of 

 fourth vein proximad of anterior crossvein with bend. Halteres 

 yellowish brown or brown. 



Abdomen: Tergites shmmg, rugose, wholly blackish green, wholly 

 brownish yellow, or anterior tergites yellowish and posterior tergites 

 blackish, the extent of each color rather variable. Disc of first 

 tergite with pale setae. Genitalia (fig. 10, c,d) with apical part of 

 aedeagus consisting of a bulbous base and two filamentous terminal 

 tubes which are at least as long as the bulbous base. 



Females: Body length 3.5-5.0 mm.; wing length 2.5-3.8 mm. 

 Pruinose triangle on mesopleuron more distinct. Abdominal tergites 

 usually unicolorous, blackish green; if bicolorous, yellowish color 

 extends to posterior margin of third tergite. Otherwise similar 

 to males. 



Specimens examined: Arizona (2599, 25 d^d'): Chuicahua Mts. 

 (Rustler Park), Huachuca Mts. (Sunnyside Canj^on), Lakeside, 

 Santa Rita Mts.; Apr. 7-Aug. 7. California (999, 13cfcf): 

 Bishop, Boulevard, Jacumba; July 5-28. Colorado (Id^): Lyons; 

 July 9. Illinois (2d^cf): Metropolis, Olney; Ma}' 29- Aug. 5. 

 Iowa (19, ScTcf): Ames, 8 miles southeast of Britt, County 3, Des 

 Moines (Polk County), 7 miles northwest of Thompson, Sioux Cit}^ 

 (South Ravine), 5 miles south of Stanhope; June 15-Aug. 25. Kan- 

 sas (1299, ddd^d"): Clark County, Coffey County, Cowley County, 

 Douglas County, Cove County, Harper County, Hodgeman County, 

 Inman, Lyons County, Manhattan, McPherson County, Medora 

 Sand Dunes, Miami County, Montgomery County, Ottawa County, 

 Saline County, Sedgwack County, Stark; May 22-Aug. 31. Mon- 

 tana (19): No data. Nebraska (19): No data. New Mexico 

 (19, 3cfcf): Albuquerque, Las Cruces; June 4-July 3. South 



