Studies of North American Bees 35 



of a pair from that locality bears Bruner's No. 18, and is the 

 same as the male recorded as D. occidentale Cresson by Cockerel! 

 in Annals and Magasine of Natural History, series 7, V, p. 414. 

 D. zehratum is, however, quite .distinct from D. occidentale, aver- 

 aging distinctly larger in both sexes {occidentale is only 10-12 

 mm. long), while the female further differs in the presence of 

 four spots on the mesoscutellum the inner pair of which are very 

 large and oval (only two round spots on the mesoscutellum in 

 occidentale $), of distinct yellow spots externally on the tibial 

 bases (wanting in occidentale $), and of continuous and not dis- 

 cally emarginate yellow abdominal bands (interrupted on tergite 

 I and emarginate on disks 1-3 in occidentale 5), while the male 

 further differs in having the lateral face marks much more 

 abruptly narrowed at level of insertion of antennae, being con- 

 tinued upward as a mere line contiguous to orbit (broadly so in 

 occidentale J*), in having always two large yellow spots on 

 the mesoscutellum and usually also two smaller yellow dots 

 outside this pair (mesoscutellum wholly black in occidentale J*), 

 in having the anterior femora almost always with an extensive 

 yellow stripe or area beneath (lacking in occidentale ^), in 

 having the abdominal bands not emarginate on first four tergites 

 or but very feebly so on first two or three (distinctly emarginated 

 bands on tergites 1-4, deeply so on i and 2, in occidentale ^), and 

 having the pygidium usually with a yellow spot, subtriangular, 

 and terminating in a stout, blunt median spine while the sides have 

 prominent angles {occidentale J* has the pygidium black, medially 

 carinate, and terminating medially in a broad shallow sinus). 

 The female of D. aehratnm has never been described but may 

 readily be known by the characters given in the above comparison 

 with occidentale, and the diagnosis given in the table. The allo- 

 type was collected by the writer at Glen, Sioux county, 4,000 feet, 

 August 18, 1906 on Gutierresia sarotlirae in company with typical 

 males. 



Among the other Heteranthidium, zehratum is closest to chip- 

 pewaense Graenicher, but differs in the male by the presence 

 of the yellow spots on the mesoscutellum, the always complete 

 band on tergite i, the lack of distinct emargination anteriorly on 



35 



