Studies of North American Bees 33 



very short line on posterior orbits near summits, the collar, tubercles, 

 tegulae, stripe on wing bases, lobes of mesoscutellum, line on metanotum, 

 large oblong spots on sides of propodeum, large transverse oblong bars 

 on mesopleura, two small spots on posterior mesosternum, and macula- 

 tions of legs and abdomen very pale yellow or yellowish white. Legs 

 very pale yellow, with all of the coxae except large external spots on the 

 last four, the trochanters and femora behind except a narrow apical band 

 on the trochanters and an inferior apical stripe on the anterior femora, 

 posterior tibiae behind and large areas involving most of the first four 

 tibiae behind, and last four tarsi except the outer faces of the basitarsi, 

 black, the trochanters and femora in front rather extensively suffused 

 with brownish-testaceous. Abdomen distinctly very finely and closely punc- 

 tured, tergites 1-5 medially with complete very pale yellow bands, that on 

 tergite i slightly notched laterally on anterior margin and medially grad- 

 ually narrowed to one-half of its lateral width, those on 2 and 3 very 

 broad laterally and gradually very much narrowed medially leaving large 

 semicircular (on 2) or crescentic (on 3) black basal areas, that on 4 nar- 

 rowed about as on i, that on 5 involving most of the tergite but deeply 

 medially emarginate anteriorly. Venter black with a medially interrupted, 

 very pale yellow band on sternite 3 which broadens laterally and nearly 

 encloses a black spot, sternite 4 medially with narrow lateral very pale 

 yellow stripes. Pubescence exceedingly scanty, most evident between the 

 antennae and behind the wings, all white. Wings basally subhyaline, the 

 apical margin rather heavily darkened, a clear spot beyond third submar- 

 ginal and third discoidal cells, nervures blackish, stigma rufo-testaceous. 

 Clypeus finely and rather closely punctured, the sides of the face shining 

 and shallowly, rather sparsely punctured. Vertex with fine, mostly sep- 

 arated punctures. Mesoscutum rather finely, cancellately punctured, meso- 

 pleura with coarse, shallow, close punctures. Anterior coxae with long 

 red spines. 



J'. Length 6.5-8 mm. Like the $, but the labrum, the inferior orbits 

 nearly meeting postorbital stripe behind, and the whole of the face below 

 the antennal level, except sometimes for dark lines in the lateral clypeal 

 sutures, with lateral face marks extending around antennal bases and end- 

 ing in a point near summit of orbits, very pale yellow. The mesosternal 

 spots are much larger, the coxal spots are larger, the anterior and middle 

 femora and tibiae may have black areas behind or these may be yellowish 

 or brownish behind, and only the apical joints of the middle tarsi are dark. 

 Abdominal bands on tergites 3-5 narrower and more attenuated medially, 

 6 with an apical band or two spots, sternites 3 and 4 with medially nar- 

 rowed, complete or narrowly interrupted bands, 5 sometimes with vague 

 curved lateral lines. Apex deeply notched. 



Type. — Bill Williams Fork, between Mojave and Yuma coim- 



187 



