FLIES OF GENUS RIVELLIA — NAMBA 33 



shining, rugulose, brown; parafacials and part of orbits ventral to 

 each eye brownish j^ellow. Antenna with first and second segments 

 blackened on outside, yellow inside; third segment brownish yellow 

 only on the posterior one-thu-d of inside, remainder blackened, the tip 

 pointed anteriorly. Anteclypeus dark brown. Palpi yellow. Post- 

 cranium black, lightly pruinose. 



Thorax: Mesonotum black; strong humeral and posterior dorso- 

 central setae present. Scutellum and postscutellum concolorous with 

 mesonotum. Pleura dark brown, mostly shining. Mesopleuron 

 with scattered pale setae on posterior half; pruinose area at dorsal 

 posterior corner in form of right triangle, one side reaching almost to 

 ventral posterior corner, the other almost to anterior spiracle. Sterno- 

 pleuron with a narrow pruinose strip on ventral margin and a much 

 narrower strip on posterior margin; disc with few scattered pale setae. 

 Disc of pteropleuron with scattered pale setae, one black seta present 

 ventral to subalar. Hypopleuron with shming central spot, remainder 

 pruinose. Laterotergite with shining spot on dorsal posterior corner, 

 remamder densely pruinose. Prosternum dark brown. 



Thoracic appendages: Legs with coxae, femora, and tibiae dark 

 brown; front and hind tarsi blackened from third segment, remaining 

 segments yellow; middle tarsi wholly yellow. 



Wing (fig. 7,«) length 2.9 mm., width 1.2 mm. Bands dark brown. 

 First and second bands separated at costal margin, very narrowly 

 separated in discal cell; third and fourth bands very narrowly joined 

 at costal margin. Second and third bands appear perpendicular to 

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

 cell completely banded. Section of fourth vein proximad of anterior 

 crossvein with very slight bend. A very narrow hyaline slit present 

 anterior and basad of junction of second and third veins. Halteres 

 with pedicel brownish yellow, capitulum dark brown. 



Abdomen: Tergites shining, rugose, black. Disc of first tergite 

 with pale setae. Ovipostor sheath black. 



Allotype: Male. Body length about 2.7 mm.; w^uig length 2.2 

 mm., width 1.0 mm.; first and second antennal segments not black- 

 ened on outside; genitalia (fig. 7,o) with apical part of aedeagus 

 consisting of a small bulbous base and two long filamentous terminal 

 tubes about four times the length of basal part of aedeagus. Other- 

 wise similar to holotype. 



Paratypes: Three females. Body length 3.3-4.2 mm.; wing 

 length 2.5-4.0 mm. In one specimen the front coxae yellowish brown 

 on inside. In two specimens the first and second bands of wing 

 definitely joined in discal cell and third and fourth bands broadly 

 joined at costal margin. Otherwise essentially similar to holotype. 

 Specimens: Holotype, 9, Tumicacari Mts., Ariz., July 22, 1938, 



