4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.60. 



10. Front tibiae with three extremely long macrochaetae on the outer flexor 



side No. 16. protervus Melander. 



Front tibiae with a row of short bristles near the outer flexor side. 



No. 8. tenuiseta, new species. 

 Front tibiae not as above 11. 



11. Femora mostly yellow with gray or black markings 12. 



Femora mostly blackish or red 13. 



12. Front femora with a gray spot on the outside near the base; front coxae 



ashen gray in front No. 7. bipunctatus, new species. 



Front femora with a gray spot on the underside near the base ; front 

 coxae yellow in front at the apex No. 10. olympiae Aldrich, 



13. Hind femora reddish-yellow with a deep infuscation from base to apex; 



posterior cross-vein deeply bowed in center No. 6. binodatus Loew. 



Hind femora paler yellow with an infuscation on basal two thirds only ; 

 posterior cross-vein nearly straight No. 12. moechus Loew. 



1. TACHYTRECHUS SIMULATUS, new species. 



Figs. 5. 6. 



Male. — Face twice as wide on lower part as it is immediately be- 

 low the antennae ; face stops far short of lower edge of eyes ; a very 

 narrow green stripe in center, balance of face heavily coated with 

 brown dust, dull ; front dark green dusted with grayish-white around 

 the sides; ocellar triangle black, ocelli yellow. Orbital cilia and 

 mouth parts black. Antennae black, each of the three joints of 

 nearly equal length, first joint beset with black hairs above; arista 

 pale on apical half gradually thickened on lower half toward base. 

 Orbital cilia black. Thorax and scutellum green with a bronze and 

 white pruinose reflection according to the position in the light. Ab- 

 domen bright green with a white pruinosity. Hypopygium large, 

 black with dark red areas on the side, black areas with a whitish 

 pruinosity; lamellae slightly triangular, brown black, cilia black. 

 Legs coated with a whitish dust the entire length, femora green, 

 knees reddish-yellow ; tibiae and tarsi darker reddish-yellow, a slight 

 infuscation at apex of tibiae and on the tarsal joints. Wings broadly 

 rounded at apex (much broader than in vorax) large black dot in the 

 apex, most of which is behind the fourth vein and the dot is de- 

 cidedly pointed behind, tip of wing has a long, narrow, snow-white 

 spot ; tegulae deep yellow, cilia long and black ; halteres deep yellow, 

 slightly infuscated at base. 



Length 5 mm. 



Female. — Like the male except it is slightly more robust; face 

 and front slightly paler; wings with a small brownish cloud at the 

 apex. This is the only female in the genus with a wing maculation. 



Type locality. — St. Anthony, Idaho, July 16, Dr. J. M. Aldrich, 

 collector. 



Described from three males and one female. 



