44 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loe 



Abdomen: Tergites shining, smooth, yellowish brown toward 

 base of abdomen, blackish toward tip. Disc of first tergite with pale 

 setae. Genitalia (fig. 3,c,d) with apical part of aedeagiis little shorter 

 than basal part. From dorsal view apical part with lateral margins 

 subparallel basally, converging apically. 



Paratype: One male; body length about 3.2 mm.; wing length 

 3.0 mm,, width 1.4 mm.; halteres with pedicel yellow, capitulum 

 brown; fore tarsi blackened from third segment, middle tarsi with 

 fifth segment blackened, hind tarsi blackened from fourth segment; 

 first basal cell faintly banded at base; second and third bands joined 

 in discal cell. Otherwise similar to holotype. 



Specimens: Holotj^pe, cf, Atlanta, Ga., June 27, 1933, P. W. 

 Fattig (USNM 61919). Paratype: Michigan: Marble Lake, Quincy 

 (Icf , May 31, 1942, C. W. Sabrosky, CWS). 



Remarks: This species is ver}^ closely related to R. pallida. I 

 cannot separate the females of the two species. The males can be 

 separated by the genitalia. In R. imitahilis the apical part of 

 the aedeagus is little shorter than the basal part and is not appressed 

 to the basal part. In R. pallida the apical part is longer than the 

 basal part and is appressed to the basal part at its base. R. imitahilis 

 can be distinguished from other species by the wing banding, male 

 genitalia, and the yellowish color of the body. 



Rivellia tcinifredae, new species 



Figure 9,e-g 



Holotype: Male. Body length 5.2 mm. 



Head: Frons reddish brown; upper fron to-orbital plates and ocellar 

 triangle blackened. Face with little less than dorsal half pruinose; 

 remainder shining, smooth, dark brown medioventrally, with yellow- 

 ish brown 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 blackened on out- 

 side, inside yellow; third segment with tip and outside blackened, 

 remainder yellow, tip pomted anteriorly. Anteclypeus concolorous 

 with medioventral portion of face. Palpi yellowish brown. Post- 

 cranium black, pruinose. 



Thora.x: Mesonotum black; strong humeral and posterior dor- 

 socentral setae present. Scutellum and postscutellum concolorous 

 with mesonotum. Pleura black, mostly shining. Mesopleuron 

 with scattered, weak, pale setae on posterior half; pruinose area at 

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

 half way to ventral posterior corner, the other side reaching half way 

 to anterior spiracle. Sternopleiiron with narrow pruinose strip 



