Studies of North American Bees 103 



Malvastruni coccincum, Cornus stoJonifcra and Senecio atriapi- 

 culatus, and, toward the end of the season, on Helianthiis. In a 

 series of eight females and three males from Sioux and Dawes 

 counties, Nebraska (Warbonnet, Jim creek and Indian creek 

 canyons and Crawford), the females agree with A^. martineUa 

 Ckll., to which species Cockerell has already referred a Sioux 

 county specimen (/. c., 1903, p. 590), and the males agree with 

 N. scita Cresson. It seems from a study of the evidence that 

 there is no reasonable doubt but that inartincUa is the female of 

 scita, a conclusion which Cockerell practically reached recently 

 (/. c, 191 1, p. 648), since the supposed characters of martineUa 

 (^ — ^broader abdomen and darker legs — are scarcely tangible 

 enough to indicate good species but much more probably represent 

 individual variations. A new locality record of this species is a 

 male from Dickinson, North Dakota, May 25, 1912, on Notho- 

 calais cuspidata (C. H. Waldron: Stevens No. 3307). 



Subgenus Centrias Robertson, 1903 



KEY TO THE NEBRASKA SPECIES 



FeuiaJe 



Black, the face, mandibles except tips, orbital margins sometimes meeting 

 above and extending over vertex, antenna! joints 1-3, tubercles, 

 tegulae and line above, two lines of variable length on meso- 

 scutum, mesoscutellum, irregular patch on mesopleura, legs ex- 

 cept posterior femora and tibiae behind, and more or less of 

 venter, red ; malar space, collar, axillae, metanotum and abdom- 

 inal bands on tergum, yellow, the latter broadly interrupted on 

 tergites 1-3 but continuous on 4 and 5 ; wings fuliginous, nerv- 

 ures blackish, stigma red; fringes of hair about the tubercles, 

 on collar and sides of propodeum, otherwise practically nude ; 

 lo-i I mm erigeronis. 



Male 



Black, the face, anterior orbital margin, labrum, mandibles, scape in 

 front, collar, tubercles, tegulae, patch on mesopleura, axillae, 

 middle of lobes of mesoscutellum, metanotum, much of coxae and 

 trochanters and apices of the femora and tibiae, and bands on 

 the abdominal tergites, yellow ; legs, margins of lobes of meso- 



103 



