40 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loa 



Vadnais, Oak Forest (Ramsey County), Snail Lake, St. Anthony Park, 

 Sucker Lake, University Farm; May 23-July 18. Missouri (19): 

 Parkville; May 25. New York (1399, 5cfc^): Centereacli (Long 

 Island), Flatbush (Long Island), Gowanda, Ithaca, Pocantico Hills, 

 Tuxedo (Station for Study of Insects) ; May 26-July 9. Oxtario (19, 

 1 c?) : Simcoe, Toronto; May 5-July 1. Pennsylvania (19) : Delaware 

 County; July 7. Virginia (19, 4d'd^): Great Falls, Rosslyn; May 

 2-13. 



Remarks: This species can be distinguished from other RivcUia 

 by the banding of the wings, smooth abdomen, male genitalia, and 

 the general body color. 



This species, as with R. fiavimana and R. 'pallida, is found abun- 

 dantly on hogpeanut, Amphicarpa bracteata (L.) Fernald. I had the 

 opportunity to observe the increase and decrease of the population 

 densities of these three species in a patch of A. bracteata about three 

 yards square in 1951 and 1952. Although actual counts were not 

 made, these changes in population were very evident. R. flavimana 

 was first to appear in the spring. After its population reached a peak 

 and began to dwindle R. metollica made its appearance. By the time 

 the population of R. metallica reached its peak there were few or no 

 R. fiavimana found. R. pallida appeared wdien the R. metallica 

 population began to decrease, and, as with the previous sequence, 

 there were few or no R. metallica left when the R. pallida population 

 was at its peak. 



RivelUa munda, new species 



Figure 7, a-d 



Holotype: Male. Body length about 5.0 mm. 



Head: Frons yeUow; ocellar triangle slightly blackened; upper 

 fronto-orbital plates concolorous with frons. Face with dorsal half 

 pruinose, ventral half shining, pale yellow, smooth; parafacials and 

 part of orbits ventral to each eye yellow. Antenna wholly yellow; tip 

 of third segment pointed anteriorly. Anteclypeus yellow. Palpi 

 yellow. Postcranium pale yellow, pruinose. 



Thorax: Mesonotum yellow; strong humeral and posterior dorso- 

 central setae present. Scutellum and postscutellum concolorous with 

 mesonotum. Pleura yellow, mostly shining; pruinosity obscure ex- 

 cept on sternopleuron and laterotergite. Mesopleuron wdth scattered 

 pale and black setae on posterior one-third ; sternopleuron with narrow 

 pruinose strip on ventral margin and much narrower strip on posterior 

 margin, center of disc with cluster of black setae; pteropleuron with 

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

 Laterotergite completely pruinose. Prosternum yellow. 



