2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. GO 



FolloAving Becker- I recognize two subgenera, Argyra and Leu- 

 costola. The former has the first antennal joint hairy above, while 

 it is bare in the latter. The character dwindles in value, until in 

 several species there is only one hair on the joint* All our species of 

 Leucostola have the thorax polished green with more or less silvery 

 white pollen, as in typical Argyras; the abdomen in all has consid- 

 erable yellow on the basal segments; the antennae, venation, and 

 hypopygial structures are alike in both groups. 



KEYS TO THE NORTH AMERICAN SPECIES OF THE GENTS ARGYRA 



A. Snligenus Argyra — Males 



1. Abdomen without yellow on the sides, or very nearly so 2 



Abdomen with distinct yellow ground color on some of the segments 13 



2. Anterior coxae wholly black, or nearly so 3 



Anterior coxae yellow, at least on apical half 10 



3. Hind basitarsus with long bristles 4 



Hind basitarsus with only the usual short hairs 5 



4. All femora black with their tips narrowly yellow (Washington), 



S. nigriventris, new species. 

 All femora j'ellow, except apical half of posterior pair (California), 



9, argentiventris, new species. 



5. Middle femora widened below near basal third, so as to form an obtuse 



angle; their tibiae with a brush of hairs near the middle (California), 



10, femoralis, new species. 

 Middle femora nearly evenly rounded or straight below 6 



6. All femora yellow, their base may be slightly blackened (Oregon), 



7, scutellaris, new species. 

 Fore and middle femora black; posterior pair yellow with apical third 



black (New England) 31, obscura, new species. 



All femora black, their tips may be yellow 7 



7. Face and front velvety black (Alaska; California; Washington: Idaho), 



1, nigripes Loew. 



Face white or grayish white ; front metallic green with more or less gray 



pollen 8 



8. Anterior tibiae with long hair on their posterior surface and the usual 



bristles above (California) 6, barbipes, new species. 



Anterior tibiae without long hair 9 



9. Hind tibiae wholly black; scutellum bare on the disk (Colorado). 



2, hirta, new species. 



Hind tibiae partly yellow ; scutellum with numerous hairs on the disk 



(Canada) 14, bimaculata, new species. 



10. Hind femora not at all infuscated at tip; fore coxae with only pale hairs 



and bristles (Wisconsin; Maine; New York) 4, angustata, new species. 



Tips of l;ind femora and the bristles of the fore coxae black 11 



11. Hind basitarsus with long bristles (California), 



9, argentiventris, new species. 

 Hind basitarsus with only the usual shox-t hair 12 



12. Arista three or four times as long as the third antennal joint ; black hair 



and bristles of fore coxae conspicuous (California)-- 8, cylindrica Loew. 



Arista not as long as third antennal joint; fore coxae nearly bare, except 



the bristles at tip (Louisiana) .5. brevipes, new species. 



Nova Acta, vol. 104, pt. 2, p. 74. 



