470 AMERICAN HYMENOPTERA. 



sionally partly or entirely obliterated on the sides, leaving only a black 

 spot on the disc. The center of the disc bare. Mesopleura covered 

 with yellow pile to, or very nearly to, the bases of the legs ; meta- 

 pleura with considerable yellow pile ; sides of the median segment 

 mostly dark. 



Abdomen. — Dorsum : segment one dark, but usually with a slight 

 touch of yellow on its anterior corners ; segment two dark ; segment 

 three dark, but usually with a strong touch of yellow pile on its hind 

 corners ; segment four dark on the middle (at least on the basal mid- 

 dle) and with yellow pile on the sides; segment five mostly dark, but 

 with yellow pile on the extreme sides ; segment six dark, but each side 

 with a broad and somewhat indefinite, but distinctive, line of brownish 

 pubescence. Venter dark, the apical portion of the apical segment 

 with considerable brownish pubescence. Each side of the hypopy- 

 gium with a very strongly elevated and angular process or carina, 

 visible even from the dorsal side, the two carinas converging posteriorly, 

 becoming less pronounced and disappearing near the tip of the segment . 



Wings. — Somewhat stained with brown, but not strongly so. 



Legs. — Entirely dark. Length of hind metatarsus about two and 

 one-half times its greatest width, its posterior edge strongly arcuated. 



Dimensions . — Length, 15 mm. to 19 mm. Spread of wings, 35 mm. 

 to 42 mm. Width of abdomen at second segment, 8| mm. to Qj mm. 



Redescribed from nineteen females, one of them being 

 the type and six being cotypes. 



Habitat. — I have records of this species as follows : Mon- 

 tana (Bozeman, Gallatin County, Big Fork), British Colum- 

 bia (Vancouver and Kaslo), Washington (Blue Mountains). 

 There is a specimen before me bearing the locality label 

 " Ithaca, New York," but I consider this record very ques- 

 tionable. This is apparently a pretty strictly Boreal form. 



P. ashtoni is by far the closest ally of this species, as is 

 shown by its structure. The two species may be readily 

 separated by the differences in coloration of the pleura and 

 of the fourth dorsal abdominal segment. I cannot agree 

 with Mr. Swenk in considering laboriosus more closely related 

 to latitarsiis than is insularis. 



P. insularis, which resembles this species considerably in 

 coloration, can be separated from it, as Dr. Morrill made 

 clear, by its longer malar space, its more narrow hind meta- 

 tarsi, and the less prominent lateral elevations on its hypo- 

 pygium. This species can also be separated readily from 

 campestris, as Dr. Morrill has shown. 



