1896.] NATURAL SCIENCES OF PHILADELPHIA. 81 



scape above the level of insertion of antennae, dull pale yellow. In 

 the median line the pale color is sometimes carried upward as a 

 narrow stripe about two-thirds of the distance between insertion of 

 antennae and middle ocellus. Mandibles simple, unusually stout, 

 blunt at tips, dull pale yellowish with rufous ends. Mouth parts 

 only moderately elongated. Antennae black above, yellow beneath, 

 the yellow predominating on scape, the black on flagellum. 



Mesothorax very shiny, sparsely punctured. Prothorax includ- 

 ing tubercles either entirely yellow, or the anterior and posterior 

 borders broadly yellow, leaving a narrow transverse dark band. 

 Legs entirely yellow, except hind tibiae and tarsi, which are brown- 

 ish. The middle tibiae sometimes show a brown patch. 



Tegulae yellowish hyaline. Wings hyaline, costal nervure and 

 margin of stigma dark brown, tiie other nervures practically color- 

 less. Marginal cell rather obliquely truncate, the substigmatal 

 portion about as long as poststigmatal ; 2d submarginal not or 

 hardly narrowed one-half to marginal, the degree of narrowing 

 variable ; 3d discoidal distinct. Abdomen above black, with five 

 very regular yellow bands, the first slightly interrupted. The black 

 and yellow are nearly of equal width, so that the abdomen might be 

 said to be alternately black and yellow-banded. Venter entirely 

 yellow with an orange tinge. 



$ . — Length 4 mm. Cheeks unarmed. More pubescent, antennae 

 more yellow. Mandibles pointed but not slender, the shining 

 rufous tips very distinctly separated from the yellowish portion. 



Face all pale yellow up to level of antennae, the yellow extending 

 further upward, in the median line as a narrow mark of the shape 

 of a spear-head, scarcely the length of the scape, and at the sides 

 about the length of the scape along orbital margiq, but very obliquely 

 truncate, and notched on its inner side below the truncation. Pro- 

 thorax with more black. Mesothorax and scutellum bluer. Hind 

 femora with a dark brown patch near the end. Nervures brown ; 

 3d discoidal very indistinct. 



Abdomen above with only four bands; these narrower, and 

 divided or deeply notched in middle. Sometimes the abdomen has 

 only three bands. 



Hab. — Las Cruces, N. M., in the town, numerous at flowers of 

 narrow-leaved willow and another species of willow, May 2, May 3, 

 May 5, 1895. They are associated on the willows with Halictus, 

 Andrena and Prosopis. 



