240 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 41. 



the yellow ending in a point, away from the orbit, a short distance 

 above the antennae; lower half of posterior orbital margins broadly 

 yellow; scape thick, very broadly yellow in front; flagellum long 

 (reaching postscutellum) and thick but normal, black above except 

 at apex, broadly bright ferruginous beneath; third antennal joint 

 much shorter than fourth; mesothorax black, densely and coarsely 

 punctured ; metathorax all black ; upper border of pro thorax, tubercles 

 and coarsely punctured tegulas, bright yellow; scutellum bigibbous, 

 with two very large contiguous round patches, ferruginous suffused 

 with yellow; postscutellum with a short band of the same color; 

 pleura with a broad angular (rather L-shaped) yellow patch in front, 

 a reddish-yellow spot near the middle of the upper part, and a small 

 spot near the lower end posteriorly ; legs red marked with yellow, and 

 with the anterior tibise in front, and the outer side of the hind basi- 

 tarsi, all yellow; wings strongly yellowish, dusky at apex; b. n. a 

 little basad of t. m.; second s. m. broad below, receiving first r. n. 

 about middle; stigma and nervures clear ferruginous; abdomen 

 broad, bright yellow, basal half of first segment black, and a triangu- 

 lar red lobe projecting from the black in the middle, reaching the 

 middle of the yellow band; hind margins of segments reddish sub- 

 hyaline, and extreme bases black; apical plate large, shallowly emar- 

 ginate; venter yellow, only the basal part darkened. 



Habitat. — Los Pinos, Colorado, at flowers of Erigeron, May 22, 1899 

 (Carl F. Baker). 



Type.—Csit. No. 14022, U.S.N.M. 



In my table of Rocky Mountain Nomada this runs to 47, differing 

 from N. superba by the notched apical plate. The following table 

 brings out its relationships with the species running to the same 

 point in the 1903 table: 



Large and robust; metathorax with an obtuse projecting angle on each side; post- 

 scutellum all black; hind margins of abdominal segments black (male). 



superba Cresson. 

 Smaller; metathorax without such angles 2 



2. Outer nervures dark fuscous; first r. n. joining second s. m. far beyond middle; 



scutellum with large yellow spots; postscutellum with a yellow band; hind 



margins of first four abdominal segments black (female) viimula Cockerell. 



Outer nervures ferruginous or light brown: first r. n. usually joining second s. m. 

 about middle (beyond in crawfordi) 3 



3. Legs red, strongly marked with yellow; postscutellum with a light mark; lateral 



face-marks very broad above xantholepis Cockerell. 



Legs red, not or hardly at all marked with yellow; postscutellum all black 4 



4. Lateral face-marks broad above crawfordi Cockerell. 



Lateral face-marks narrow above ednae Cockerell. 



N. xantholepis is a typical member of the subgenus XantTiidium 

 Robertson. Superficially, it looks very much like N. civilis Cresson. 

 In the table ^ it runs out next to N. sandxcrucis Cockerell. 



» Proc. Acad. Nat. Sci. Phila., 1903, p. 580, 



