AMERICAN DIPTERA. 225 



7. Tibiae and knob of halteres yellow portsecola Walker. 



Tibiae and halteres black Wiutheiiii Zetterstedt. 



8. Front femora marked with black 9. 



Front femora wholly yellow postiva Walker. 



9. All the tihise yellow f'enestrata Say. 



Middle and hind tibise more or less black similis Walker. 



10. Legs wholly black 11. 



Legs more or less yellow 12 



11. Wings with a black spot at last third of costal margin. 



inaciilipeniiis Walker. 

 Wings infnmated, except the whitish base clavipes Loew. 



12. Anal cross-vein wanting piisilla Loew. 



Anal cross-vein present 13. 



13. Legs yellowish rostrata Loew. 



Legs somewhat darkened rapax Loew. 



14. Marginal cell obliquely truncate; fifth vein ending in hind margin at the 



base of the outer dark cross-band enecator sp. nov. 



Marginal cell narrowed to the tip; fifth vein recurved, ending in the clear 

 space Schwarzii Coquillett. 



Tachydroinia Schwarzii Coquillett (Fig. 52). 

 Proc. Nat. Mas., 1895, p. 440. 



Shining, black. Head opaque gray poUinose, the cheeks shining. AntenuEe 

 fuscous, the third joint short, conical, the apical arista bristle-like, four times as 

 long as the antenna. Legs dark brown, the bases of the tibiae and of the tar.si, 

 and sometimes of the femora, yellowish. Knob of the halteres whitish. Wings 

 whitish, crossed by two broad brown bands, the first extending from the base of 

 the second vein to slightly beyond the posterior cross-vein, the second extending 

 from slightly beyond the apex of the fifth vein to a short distance beyond the 

 tip of the second vein, leaving the base of the wing, a cross-band just beyond the 

 middle and the tip of the wing whitish ; anal cross-vein wanting, the other two 

 of an equal length, the distance between them subequal to that between the 

 small cross-vein and the base of the third vein, the second l)asal cell longer than 

 the first by twice the length of the cross-vein; distance between the tips of the 

 third and fourth veins equal to one-third of that between the second and third 

 veins; marginal cell about one-half as wide as the subuiarginal. 2.5 mm. 



California, Utah, Idaho, Texas; Guerrero, Mexico. 



This is not an uncommon species, as there are numerous specimens 

 in the collection. 



The apex of the marginal cell is gradually narrowed by an even 

 curve of the second vein ; the fifth vein terminates between the 

 middle and the outer edge of the central clear band. 



The two males from x\ustin, Texas, differ from typical examples 

 of Schwarzii in their coloration. The cross bands of the wings are 

 dark plumbeous instead of brown, and the lighter parts of the legs 

 are white instead of brownish. These specimens were running over 



TRANS. AM. ENT. SOC, XXVIII. (29) JULY. 1902. 



