1923] 
The Genus Cyrtopogon 
103 
2. Third antennal joint red; mystax largely white or yellow;, 
(if halteres are blackish and face has white hairs, see 
longimanus; if large species with base of abdomen densely 
pilose, see dasyllis) 3 . 
Third antennal joint black 11. 
3. Tibiae and tarsi more or less reddish. . 4. 
Legs black; claws white with black tip 10 . 
4. Pile of scutellum and hypopleurae white; apex of femora 
reddish; mystax mostly white; pile of tibiae and pleurae 
very long. (Can., N. H., Ct., N. Y., Mass., Va., N. C. 
marginalis Lw . 
Pile of scutellum black; of hypopleurae more or less black; 
femora black ; western species 5 . 
5. Front tibiae and tarsi of male silvery pilose on posterior 
side; wings hyaline 6 . 
Legs not silvery, but sometimes with yellowish white hairs 
fringing tarsi; pile of male abdomen more or less tufted; 
wings with light clouding about veins, anterior crossvein 
near base of discal cell 7 . 
6. Male: front tibiae with fine white silky pile on outer side, 
becoming longer and denser apically; front tarsi with 
silvery hairs on anterior side of joints 2-5 in addition to 
the silvery hairs on posterior side; abdominal segments 
1, 2 with pale yellow pile, longer on sides, remaining segments 
with very short hair, yellowish on 3, black on rest, 
segments 2-5 white-fasciate, interrupted on 4, 5. 
(Col.) pulcher Back 
Male: front tibiae with moderately long silvery pile pos- 
teriorly, short yellow pile anteriorly; front tarsi with 
yellow hairs on anterior side of first two joints; abdomen 
with reddish yellow pile forming dense apical bands on 
segments 1-4, segments 2-4 silvery fasciate. (Alta.) 
(Can. Ent. liv. 278, 1922) albitarsis Curran. 
7. Pile of abdomen yellow or fulvous at least on first segment, 
tip of male abdomen blue-black, segments 2-4 with com- 
plete fasciae, sometimes hidden by dense pile in male; 
basal half of claws reddish 8 . 
