48 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loe 



Swannanoa; Jul}^ 10-Aiig. 16. Virginia (2 9 9, Icf): Great Falls; 

 June 12. New Jersey (1 9 , 1 d') : Westfield, West Orange; June 18- 

 Sept. Ohio (19, IcT): Summit County; June 19-28. Pennsyl- 

 vania (19): Lehigh Gap; July 9. New York (16 9 9, 12d^cf): 

 Ithaca, Babylon, Mosholu, Bronx, Pocantico Hills, Flushing, Olcott, 

 Buffalo; June 9-Aug. 5. Massachusetts (2 9 9 , 5 cT cf) : East Glou- 

 cester, Boston, Woods Hole; June-Aug. 3. Quebec (2 9 9 , 3cf cT): 

 Abbotsford; Aug. 24. Michigan (219 9, 15cfcf): East Lansing, 

 Huron County, Ionia County, Midland County, Cheboygan County, 

 Genesee County, Gratiot County, Deerfield Township (Lapeer 

 County), Detroit, Hamburg, Douglas Lake, Mecosta County, Mont- 

 calm County, Muskegon County, Oakland County, Wexford County; 

 June 11-July 15. Ontario (299, IcT): Brittania, Leamington; 

 June 10-July 23. Minnesota (19, dd'd'): Sucker Lake, Kamsey 

 County; June 18-20. 



One character which separates this species from all other Rivellia is 

 the presence of strong humeral setae and the absence of the posterior 

 dorsocentral setae. 



Rivellia cognata Cresson 



Figure 10, i-/ 

 Rivellia cognata Cressou, 1919, p. 191; 1924, p. 228. 



Type locality: Swarthmore, Pa. (ANSP). 



Males: Body length 2.8-4.5 mm. 



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

 and ocellar triangle blackened. Face with dorsal half pruinose, 

 ventral half shining, smooth, dark brown or almost black; parafacials 

 and part of orbits ventral to each eye brownish yellow. Antenna, 

 with first and second segments brownish yellow; third segment with 

 tip, outside, and anterior side of inside blackened, remainder yellow, 

 the tip pointed anteriorly. Anteclypeus conclorous with ventral 

 portion of face. Palpi brownish yellow or brown. Postcranium dark 

 brown or black, pruinose. 



Thorax: Mesonotum dark browTi or blackish blue; strong humeral 

 and posterior dorsocentral setae present. Scutellum and postscutellum 

 concolorous with mesonotum. Pleura dark brown or black, 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 two-thirds distance to ventral posterior corner and the 

 other side reaching two-thirds distance to anterior spiracle. Sterno- 

 pleuron with a narrow pruinose strip on ventral corner and a narrower 

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

 pteropleuron with scattered pale setae, black setae present or absent 

 ventral to subalar. Hypopleuron with shining central spot, remainder 



