Studies of North American Bees 51 



lateral stripes, tergites 2, 3 and 4 with small yellow lateral spots (only 

 on sides of 2 and 3 in ultimella), the extreme sides of abdominal 

 sternites 2-4 with small linear yellow marks and distinct yellow spots 

 on sides of 5 (all lacking in ultimella), the third antennal joint some- 

 what shorter, obviously shorter than fourth but over half its length. 



Tv/T.— Pullman, Washington, May 14, 1898 (C. V. Piper, 

 probable collector), $. 



The type of this form is certainly very close to A^. ultimella 

 but differs from the description of the unique type of that species 

 in the above color characters, which, together with the remoteness 

 from the known range of typical nItimeUa (southern California), 

 have encouraged me to separate it as a distinct geographical race. 

 From the erythraea-taraxacella-iiltima-nicdiana group this differs 

 at once in the longer third antennal joint, which is distinctly less 

 than half as long as the fourth in the species mentioned, but dis- 

 tinctly more than half as long in both this form and typical 

 v.-ltimella. This form further differs from erythraca, mediana 

 and ntbrica in having the outer side of the hind tibiae strongly 

 tuberculate and forming an obviously roughened line in profile, 

 while in the species mentioned the tibiae are smooth. The 

 female of taraxacella has the hind tibiae tuberculate on the outer 

 side, but not so strongly so as in the above species, while ultima 

 is further distinguished by the trilineate mesoscutum and black 

 at sides of abdomen. From astori it differs in the lack of 

 mesoscutal stripes or black at base of abdomen, and in the 

 possession of yellow spots on the abdomen, and in the first two of 

 these characters it differs also from N. oregonica. Its affinities 

 apparently lie close with A^. rhodosoma and N. rhodosomella, 

 with which species it agrees in both antennal structure and tibial 

 tuberculation, but both of these lack the yellow spots on sides of 

 tergites 2—4 and the yellow at lower corners of the face, and in 

 the types of both these forms the apex of the hind tibiae ends 

 in about four very short, straight, dark bristles while in septen- 

 trionalis the tibiae end in two curved black bristles of considerably 

 greater length and stoutness. In this character it resembles A^. 

 bisetosa, described on a previous page, but that species differs at 

 once in its finely punctured clypeus and entirely red face and 



51 



