34 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



120. Middle and hind femora each with two preapical bristles. 



No. 108, renidescens Melander and Brues. 

 Middle and hind femora each with one preapical bristle 121. 



121. Second antennal joint wholly black No. 117, porphyrops, new species. 



Second antennal joint yellow with the upper edge narrowly black 122. 



122. Hind tibiae black at tip for nearly one-fourth their length. 



No. 114, reflectus Aldrich. 

 Hind tibiae only a little blackened at tip No. 113, marginatus Aldrich. 



123. Fore coxae with a green or black stripe on outer posterior edge, which is wide 



above and tapers to a point near the tips of the coxae 124. 



Fore coxae considerably blackened at base 125 



Fore coxae wholly yellow, except sometimes a blackish spot at base on outer 



surface 126. 



124. Hind femora with a row of bristles of increasing size, ending in the usual pre- 



apical bristle No. 182, aldrichii Wheeler. 



Hind femora with only one preapical bristle No. 165, penicillatus, new name. 



125. Fore coaxe nearly half black No. 116, pilatus, new species. 



Fore coxae mostly black; hind tibiae black at tip for about one-fifth their length. 



No. 121, obcordatus Aldrich. 

 (The female of pollex Osten Sacken, No. 120, probably goes in here and is likely 

 to differ from that of obcordatus in having the black at tip of hind tibiae more 

 extensive.) 



126. Antennae wholly black, or nearly so 127. 



First antennal joint distinctly yellow below 128. 



127. Length about 3 mm.; dorsum of thorax bronze brown with brown pollen. 



No. 99, brunneus Aldrich. 

 Length 4.5 mm. ; dorsum of thorax metallic green. . .No. 102; melanocerus Loew. 



128. Middle basitarsi with a conspicuous bristle above 129. 



Middle basitarsi without a bristle above 132. 



129. Middle tibiae with only one bristle below No. 117, porphyrops, new species. 



Middle tibiae with three bristles below, two near apical and one near basal 



third 130. 



130. Bristle on middle basitarsi rather small; third vein bent backward so as to 



approach fourth at tip No. 94, canadensis, new species. 



Bristle on middle basitarsi large; tips of third and fourth veins not convergent, 131. 



131. Bend in last section of fourth vein distinctly before its middle (eastern species). 



No. 105, deconis, new species. 

 Bend in last section of fourth vein very near its middle (N. Europe; Alaska). 



No. 119, plumitarsis Fallen. 



132. Middle tibiae ^vith more than one bristle below 133. 



Middle tibiae with only one bristle below 134. 



133. Middle tibiae with three bristles below, two at apical, one at basal third: fore 



tarsi black from the tip of the first joint No. 94, canadensis, new species. 



Middle tibiae with two bristles below, one near apical third and one near the 

 middle No. 191, sicarius, new species. 



134. Fore tarsi yellow with the fifth joint black, or wholly yellow. 



No. 191, sicarius, new species. 

 Fore tarsi black from the tip of the first joint 135. 



135. Fore tibiae with two large bristles below; rather large species with large bristles 



on the tibiae No. 106, setosus Loew. 



Fore tibiae with only small bristles below: rather small species 136. 



136. Fifth joint of fore tarsi yellowish, paler than those preceding it. 



No. 89, socius Loew. 

 Fore tarsi black from the tip of the first joint 137. 



