56 PROCEEDINGS OF THE NATIONAL MUSEUM vol. m 



Dakota (19, Icf): Elk Point, 3 miles south of Jefferson; June 

 11-20. Texas (1 c? ) : Glen Rose; May 19. 

 Remarks: This species is closely related to R. severini. 



Rivellia severini Blanton 



Figure 10,e-h 

 Rivellia severini Blanton, 1937, p. 139, fig. 1. 



Type locality: Winner, S. Dak. (USNM 51444). 



Males: Body length 3.5-5.0 mm. Wing (fig. 10,e) length 2.6-3.5 

 mm. Fourth band broad, width at tip of third vein equal to or 

 longer than length of posterior crossvein. Hind tibiae biown to 

 almost black. Genitalia (fig. 10,g,h) with apical part of aedeagus 

 consisting of a bulbous base and two filamentous terminal tubes 

 which are definitely shorter than length of bulbous base. Otherwise 

 similar to R. micans. 



Females: Body length 3.8-4.7 mm., wing length 2.8-3.5 mm. 



Specimens examined: Colorado (799, 13cfcf): Las Animas, 

 Lyons, Maybell, Valmont (White Rocks); June 17-July 9. Idaho 

 (299, 3cf cf): Bliss, Burley; June G-July 7. Iowa (1399, Sd'cT): 

 County 3; June 15-July 3. Kansas (19, IcT): Douglas Count}^, 

 Hamilton County; no date. Manitoba (899, 4<:fcf): Awenie; 

 July 1-28. Nebraska (499, 20^0"): Valentine; June 9-11. South 

 Dakota (599, 8c?'cf): Brookings, Canton, Elk Point, Lake Andes, 

 Newell, Winner; June 12-July 4. Utah (299, 4cf cf): Antimony, 

 Hooper, Midvale, Provo, Spanish Fork, Woods Cross; June 10- 

 Aug. 1. Wyoming (499, 8cf cf): Bull Lake, Laramie, Little Wing, 

 Lusk, Sage Creek; July-Sept. 4. 



Remarks: This species is closely related to R. micans, from which 

 it can be distinguished by the broader fourth band, usually darker 

 hind tibiae, and the shorter terminal tubes of the apical part of the 

 aedeagus. 



Rivellia Jlavimana Loew 



Figure 4,?',y 



Rivellia Jlavimana Loew, 1873, p. 92, pi. 8, fig. 7. — Hendel, 1914a, p. 177.— Cresson, 

 1924, p. 227. 



Type locality: Nebraska (MCZ). 



Body length, males, 3.0-4.8 mm.; females, 3.5-5.0 mm. 



Head and thorax: wSimilar to R. metallica. 



Thoracic appendages: Front legs: Coxae, femora, and tibiae 

 yellow; tarsi blackened from third or fourth segment, remaining 

 segments yellow. Middle legs: Coxae black; femora yellowish at 

 extreme tip, remainder black; tibiae slightly blackened at base, 

 yellowish toward tip ; tarsi wholly yellow or only fifth segment shghtly 



