64 PROCEEDINGS OF THE NATIONAL MUSEUM vot. loe 



16, 1938; 1 cf , Aug. 9, 1933; 1 cf , Jiily27, 1933; 2cf cf , Aug. 14, 1934; all 

 collected by W. Stone). South Carolina: Manning (1 9 , May 29, 

 1930, W. Stone). Texas: Victoria (1 9 , June 1924, J. D. Mitchell). 

 Virginia: (Ic^, Aug. 20, 1882). (In SEC, NC, CU, CAS, AMNH, 

 USNM, CAN, UM, and ANSP.) 



Remarks: This species can be distinguished from the other Rivellia 

 by the absence of the humeral setae, yellowish color of the head and 

 thorax, and the male genitalia. 



Rivellia steyskali, new species 



Figure 4,fc-n 



Holotype: Male: Body length about 4.2 mm. 



Head: Frons brown, upper fronto-orbital plates and ocellar tri- 

 angle black. Face with dorsal half pruinose, ventral half shining, 

 smooth, dark brown; parafacials and part of orbits ventral to each eye 

 brownish yellow. Antenna with first and second segments yellow; 

 third segment with tip and outside blackened, remainder yellow, the 

 tip pointed anteriorly. Anteclypeus concolorous with ventral portion 

 of face. Palpi dark brown. Postcranium black, pruinose. 



Thorax: Mesonotum black; strong humeral setae absent, posterior 

 dorsocentral setae present. Scutellum and postscutellum concolorous 

 w4th mesonotum. Pleura black, mostly shining. Mesopleuron with 

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

 corner in form of right triangle, one side reaching ventral posterior 

 corner, the other side almost attaining anterior spiracle. Sterno- 

 pleuron with narrow pruinose strip on ventral margin and a much 

 narrower pruinose strip on posterior margin ; disc with scattered pale 

 setae. Disc of pteropleiiron with scattered pale setae, one black seta 

 present ventral to subalar. Hypopleuron mostly shining, borders 

 narrowly pruinose. Laterotergite completely and densely pruinose. 

 Prosternum black. 



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

 low; tarsi slightly blackened from third segment, remaining segments 

 yellow. Middle legs: Coxae brown; femora and tibiae yellow; tarsi 

 blackened from third segment, remaining segments yellow. Hind 

 legs: Coxae brown; femora yellow; tibiae brownish yeUow, tarsi yel- 

 low, blackened from third segment, remaining segments yellow. 



Wing (fig. 4,^*) length 3.3 mm., width 1.3 mm. Bands black. 

 First and second bands definitely joined at costal margin; third and 

 fourth bands joined at costal margin. The part of first basal cell 

 contiguous to second basal cell banded on about basal two-thirds, 

 apical one-third hyaline, this hyaline area wedgelike basally. Section 



