58 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ioa 



Remarks: According to Mr. E. Sdguy, the type of this species is 

 "d6truits d^finitivement." 



This species stands apart from the rest of the Rivellia species. The 

 neat, slender appearance of body, anteriorly protruding head, absence 

 of both strong humeral and posterior dorsocentral setae, and the 

 presence of a pair of strong anterior dorsocentral setae, weak lateral 

 scutellar setae, and the definitely pruinose abdominal tergites make 

 this species unique among the Rivellia. 



Rivellia socialis, new species 



Figure 10, m 



Holotype: Male. Body length about 5.2 mm. 



Head : Frons reddish brown; ocellar triangle blackened, upper fronto- 

 orbital plates concolorous with frons. Face with dorsal half pruinose, 

 ventral half shining, smooth, dark brown; par afacials and part of orbits 

 ventral to each eye brownish yellow. Antenna with fu-st and second 

 segments brownish yellow; third segment brown, yellow only on inside 

 at base, the tip pointed anteriorly. Anteclypeus black. Palpi brown. 

 Postcranium black, pruinose; more convex than other Rivellia except 

 R. boscii. 



Thorax: Mesonotum black; strong humeral and posterior dorso- 

 central setae absent. Scutellum and postscutellum concolorous with 

 mesonotum. Pleura black, mostly shining. Mesopleuron with 

 scattered pale setae on posterior half; pruinosity reduced to small spot 

 at dorsal posterior corner. Sternopleuron with narrow pruinose strip 

 on ventral margin and a much narrower strip on posterior margin; 

 disc with scattered pale setae. Disc of pteropleuron with scattered 

 pale setae, few black setae present ventral to subalar. Hypopleuron 

 with shining central spot, remainder pruinose. Laterotergite com- 

 pletely and densely pruinose. Prosternum black. 



Thoracic appendages: Coxae, femora, and tibiae of all legs black; 

 all tarsi gradually blackened toward tip after first segment, first 

 segment yellow. 



Wing (fig. 10,m) length 3.5 mm., width 1.3 mm. Bands black. 

 First and second bands defmitely 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 hyahne, this hyaline area wedgelike basally. Section 

 of fourth vein proximad of anterior crossvein with definite bend. 

 Hal teres brown. 



Abdomen: Tergites black, appear pruinose, except for shining 

 medial transverse band on first-second syntergite, this band broadened 

 laterally. Disc of fu-st tergite with pale setae. Genitaha similar to 

 that of R. steyskali. 



