54 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loc 



easily distinguishes it from R. maculosa. The males of R. texana can 

 be easily distinguished from those of R. vaga by the genitalia. The 

 notable difference is the presence in R. texana and the absence in 

 R. vaga of lateral finlike structures on the apical part of theaedeagus. 

 I am not able to separate the females of these two species in all cases. 

 R. texana females are generally larger, the fourth band of the wmgs 

 usually is not connected to the thu-d band at the costal margin, the 

 sterno'pleuron usually with a medial pruinose band, and the abdominal 

 tergites are dark brown or black. R. vaga females are usually smaller, 

 the fourth band of wmg is usually narrowly connected to the thu-d 

 band at costal margin, stornopleuron without medial prumose band, 

 and abdominal tergites sometimes yellowish anteriorly. 



Rivellia micans Loew 



Figure I0,a-d 



Rivellia micans Loew, 1873, p. 94— Van Der Wulp, 1898, p. 382, pi. 10, fig. 9.— 

 Hendel, 1914a, p. 181.— Cresson, 1924, p. 228. 



Type Locality: Texas (MCZ). 

 Males: Body length 3.1-5.0 mm. 



Head: Frons reddish brown or yellowish brown; upper fronto- 

 orbital plates and ocellar triangle blackened. Face with dorsal half 

 pruinose, ventral half shinning, smooth, brown or dark brown medi- 

 oventrally, with brownish yellow lateral strip on each side which 

 terminates just before oral margin; parafacials and part of orbits 

 ventral to each eye brownish yellow. Antenna with first and second 

 segments yellow; third segment with tip, outside, and anterior side 

 of inside blackened, remainder yellow, the tip pointed anteriorly. 

 Anteclypeus concolorous with medioventral portion of face. Palpi 

 brown \nth yellow borders or wholly brownish yellow. Postcranium 

 blackish green, pruinose. 



Thorax: Mesonotum blackish green; strong humeral and posterior 

 dorsocentral setae present. Scutellum and postscutellum concolorous 

 with mesonotum. Pleura dark brown or blackish green, mostly 

 shining. Mesopleuron with scattered pale setae on posterior half; 

 pruinose area at dorsal posterior corner in form of a right triangle, 

 one side reaching halfway to ventral posterior corner and the other 

 side reaching halfway to anterior spiracle. Sternopleuron with ven- 

 tral corner and very narrow strip on posterior margin pruinose ; disc 

 with scattered pale setae. Disc of pteropleuron with scattered pale 

 setae, black setae present or absent ventral to subalar. Hypo- 

 pleuron with shining central spot, remainder prumose. Laterotergite 

 completely and densely pruinose. Prosternum black. 



