THE CANADIAN ENTOMOLOGIST 53 



least as having arisen from the same stock that produced the latter. 

 Compared with albipennis the three species under consideration 

 all show a reduction of the yellow markings, in which the face, the 

 legs and the abdomen are mainly involved ; so far as the reduction 

 of the face marks is concerned, canadensis has reached the point, 

 where the face is entirely free of yellow. 



The species mentioned above favour, so far as their habits 

 are known, flowers that are typical elements of the Prairie Pro- 

 vince. According to Pound and Clements 5 the vegetation centre 

 of the prairies is situated in Nebraska, Iowa, Kansas and the 

 Dakotas, and as one moves away from this centre in a northerly or 

 southerly direction, a decrease in the number of characteristic 

 plant species is noticeable. The Prairie Province, as defined by 

 Pound and Clements forms a broad strip, bounded on the west by 

 the Rocky Mountains, and extending from the Canadian Provinces 

 Athabasca, Alberta, Saskatchewan, Assiniboia and Manitoba 

 down through Montana and North Dakota and the states south of 

 these into Texas. From this strip an arm runs off eastwardly 

 through southern Minnesota and Iowa into southern Wisconsin, 

 northern Illinois and a very narrow portion of western Indiana. 



The known range of albipennis occupies a part of the vegeta- 

 tion centre (South Dakota and Nebraska), and passes through 

 Colorado and New Mexico into Texas. It occurs, according to 

 Swenk and Cockerell, all over the State of Nebraska, while lactei- 

 pennis covers the western part of that state only. Canadensis is 

 an inhabitant of the most northern outposts of the Prairie Province, 

 and pallid ipennis is a species of the eastern extension of the prairies 

 in Wisconsin and Illinois. As regards the distribution of this 

 species in Wisconsin, attention is called to the fact that floral 

 elements of the prairie extend their range northward to the sandy 

 areas along the St. Croix River, the so-called "pine-barrens." At 

 the mouth of the Yellow River (a tributary of the St. Croix) in the 

 northern part of Burnett Co. (latitude about 46°) there is quite 

 an assemblage of prairie-plants, and this, the type locality of 

 pallidipennis, marks the most northern point at which the bee has . 

 been found. 



5. Bot. Gaz., Vol. 25, pp. 381-394 (1898). 



