Studies of Xortli .luicrican Bees 3 1 



thin and scattered pale hairs, exceedingly short on mesoscutuni. somewhat 

 longer and deiVser on propodeuni and hind coxae, the margins of the 

 apical tergitcs and sternites witli tliin pale fringes, segment 5 with long 

 hiack bristles, scattered and straight on tergum but grouped into two 

 curved clumps ventrally. Abdomen immaculate red, tergite i impunctate, 

 2 and following with distinct, though weak and sparse, round punctures 

 except the broad shining impunctate apical margins of tergites 2-4. 

 Sternites 2-4 have the apical margin broadly shining and impunctate, 

 and the middle of 5 is similar but has the surface microscopically tesse- 

 late. while its sides and the bases of the other sternites are coarsely but 

 weakly punctured. Wings slightly yellowish, apically darkened, nervures 

 and stigma yellowish brown, basal nervure interstitial with transverso- 

 medial nervure but distinctly on the basad side, second submarginal much 

 narrowed above, narrower than the third. 



Type. — Harrison, Sioux county, Nebraska, June i, 1910, on 

 Seuecio piirshianus (M. H. Swenk), $. 



Of the described species this one seems closest to N . rhodosoma 

 Ckll., known from California and Nevada, though because of an 

 unfortunate series of chiefly comparative descriptions the real 

 characters of rhodosoma are not very apparent in the literature; 

 to be specific, the original description of A^ rhodosoma is largely 

 based on comparisons with N . erythraea, and the same author's 

 diagnosis of erythraea is largely comparative with N. ultima, 

 while the original description of N. ultima is a comparative one 

 with y. oregonica, which, finally, is described on a non-com- 

 parative basis but which is not a very closely related species. 

 Following out the characters to be gleaned from a careful study 

 of these comparisons and referring these characters to bisetosa 

 about the only discoverable difference is that rhodosoma has a 

 black stain in the middle of the enclosure which is lacking in 

 bisetosa. In the same way, the next most allied species, .V. 

 rhodosomella Ckll., is based simply upon a comparative descrip- 

 tion with rhodosoma, but from this description it is obvious that 

 bisetosa dififers from rhodosomella in the unstriped mesoscutum, 

 red upper metapleural plate, dark spot on apex of enclosure and 

 somewhat larger size. An actual study of the types of rhodo- 

 soma and rhodosomella in the U. S. National Museum (Cat. 

 Nos. 13167 and 13 161. respectively), however, shows that both 

 are distinct from bisetosa, differing chiefly in having the cInj^jcus 



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