FLIES OF GENUS RIVELLIA — NAMBA 25 



Abdomen: First five tergites with short, reclinate, black setae. 

 Ninth tergite and cerci of males covered with setae. 

 Pruinosity on the various parts of body white. 



Key^to the^species of Rivellia of America^north of Mexico 



1, Strong humeral setae present 2 



Strong humeral setae absent 25 



2(1). Posterior dorsocentral setae absent R. variabilis Loew 



Posterior dorsocentral setae present 3 



3 (2). The part of first basal cell contiguous to second basal cell completely 



banded; tip of first band joined to second band or very nearly so . . 4 



That part of first basal cell not completely banded; either not banded 



at all or partly banded; tip of first band distinctly separated from 



second band 9 



4 (3). Front and middle femora yellowish 5 



Front and middle femora dark brown or black 7 



5 (4). Second basal cell completely banded or nearly so; second and third bands 



converging, joined in the discal cell R. floridana Johnson 



Second basal cell hyahne; second and third bands subparallel .... 6 



6 (5). Third band broader than hyaline strip between second and third bands; 



no hyaline spot at junction of second and third veins. 



R. coquilletti Hendel 

 Third band narrower than hyaline strip between second and third bands; 

 a hyaline spot surrounding junction of second and third veins. 



Males, R. tersa, new species 



7 (4). Fourth band joined broadly to third band at costal margin, width of 



fourth band at that point is from costa to third vein; first, second, and 

 third bands distinctly and broadly joined together at their tips. 



R. conjuncta Loew 



Third and fourth bands joined at costal margin only between costa and 



second vein; first, second, and third bands not joined together at 



their tips, although first may be joined to second 8 



8 (7). A pair of additional strong setae present anterolateral to posterior 



dorsocentrals; hyahne spot at junction of second and third veins large, 

 covering junction and extending distad. 



Females, R. tersa, new species 

 No such setae present; hyaline spot small, not covering junction, con- 

 fined to anterior and proximad of junction. . R. australis, new species 



9 (3). Costal cell hyaline, at most very faintly banded (see alternate) but not 



darker than rest of the bands; body dark brown to black, not yel- 

 lowish 10 



Costal cell definitely banded, if faintly so, then body yellowish ... 13 

 10(9). Wing bands obsolete, consisting of faint spots 11 



Wing bands distinct 12 



11 (10). Anterior and posterior wing margins subparallel; anal angle prominent. 



R. brevifasciata Johnson 

 Wings narrowed toward base; anal angle nearly obsolete. 



R. maculosa, new species 



12 (10). Second band with section in discal cell dislocated distally; prominent 



seta present ventral to subalar; prosternum yellowish. 



R. occulta Van Der Wulp 



Second band continuous; no prominent seta present ventral to subalar; 



prosternum blackish R. metallica Van Der Wulp 



