206 THE CANADIAN ENTOMOLOGIST 



red medially, darker red apically and greenish black basally. The females 

 agree well with the original description. The spots on the first abdominal 

 segment are often absent, and the bands on the others are sometimes all in- 

 terrupted medilly. Mr. Crawford writes that he is uncertain of the validity 

 of the species. 



Perdita bruneri Cockerell. 

 Fargo, Enderlin, Sheldon, Valley City, Jamestown, Bismarck, Pleasant 

 Lake, Rugby, Minot, Schafer, Williston and Dickinson (C. H. Waldron); Aug. 

 6 to Sept. 15. A common bee and much the most common of the genus in the 

 State. Only four females were taken at Fargo previous to 1917, when it was 

 found in considerable ntimbers. Mostly at fiowers of Grindelia squarrosa; 

 also at Chrysopsis villosa, Aster muUifiorus and Helianthus petioJaris. 



Perdita swenki Crawford. 



Valley City and Pleasant Lake at Grindelia squarrosa, Chrysopsis villosa, 

 Helianthus maximiliani and Solidago canadensis; Aug. 11 and 13. Taken only 

 the two times, although iji considerable numbers at Valley City. These two 

 species determined by Prof. Cockerell some time ago as P. cockerelli Cwfd. and 

 P. bruneri Ckll. 



Perdita tridentata, new species. (Fig. 25, 1). 



Male. — Length 4 to 5.5 mm. Head and thorax greenish-blue. Yellow 

 markings as follows: base of clypeus with a broad median and narrow marginal 

 extensions, supra-clypeal spot about half as high as wide, lateral face marks 

 gradually or irregularly narrowed to a point at about the upper level of antenna! 

 sockets (see Fig. 1), mandibles except tips, scape and under side of flagellum 

 (less so on first three joints); tegular, wingbases and small spots on pronotum; 

 front half of anterior legs for their entire length, a narrower stripe on intermediate 

 ones, knees of posterior legs and often a very narrow stripe on their tibiae; bands 

 on first, fourth and fifth segments interrupted medially, those on second and 

 third slightly notched. 



Apex of clypeus, labrum, upper side of flagellum and a small spot on apex 

 of scape, light brown; legs and abdomen dark brown; wings clear but nervures 

 dark, apex of abdomen triangular but obtusely rounded. 



Type No. 6372. The type is from a series of 13 specimens taken on He- 

 lianthus petiolaris at Pleasant Lake, North Dakota, Aug. 11, 1913. Two were 

 taken on H. scaberrimus near Sheldon, Aug. 14. 1916, and one on H. petiolaris 

 at the same place Aug. 21, 1918. 



"A species of the affinis group," writes Prof. Cockerell. The abdomen is 

 very much like that of P. swenki Cwfd. The clypeal marking is somewhat 

 variable, the central extension sometimes quadrate and covering a large part 

 of the clypeus, but more commonly rounded and shorter, the lateral extension 

 sometimes nearly absent. In one specimen the clypeus is nearly all dark and 

 the abdominal bands are considerably reduced. Supra-clypeal mark often 

 notched above, sometimes almost divided. 



Perdita laticincta Swenk and Cockerell. 

 Sheldon, Pleasant Lake and Dickinson (C. H. Waldron). All at Helianthus 

 petiolaris; July 28 to Aug. 21. Prof. Cockerell has confirmed the identification 

 of this and the next two species. 



