164 HYMENOPTERA. 



Thorax. — Dorsum yellow, but with a very broad and well defined 

 black interalar band (this band being distinctly but not greatly more 

 than half as wide — from front to rear — as it is long — from wing base 

 to wing base — and of nearly equal width all the way across, though 

 slightly narrower toward the bases of the wings ; the middle of the 

 disc with a longitutinally elongate area, large enough to be very notice- 

 able to the naked eye (this area being within the black interalar band) 

 naked, mostly smooth and shining. Mesopleuraae often covered with 

 yellow pile very nearly to the bases of the legs and always with the 

 yellow extending down as far as two-thirds of the distance from the 

 level of the bases of the wings toward the bases of the legs. Meta- 

 pleurge sometimes clothed for the most part with yellow pile and some- 

 times with only their very upper ends bearing yellow hair. Sides of 

 the median segment sometimes entirely dark, but often with consider- 

 able yellow hair. 



Abdomen. — Dorsum : segment one yellow ; segment two yellow on 

 the basal middle, but with red pile on the extreme sides and along the 

 hind margin, the yellow patch narrowing toward the front margin 

 toward the sides of the segment ; segment three red ; segment four 

 with some red and a few black hairs in the very middle, at least at the 

 base, but for the most part clothed with yellow pile ; segment five 

 black, but with a few yellow hairs on the extreme sides ; segment six 

 dark. Venter usually entirely dark. Epipygium with a low, rounded, 

 longitudinal median carina on its apical portion. Hypopygium also 

 tending to be carinate on its very apical portion, in the middle. 



Wi7igs. — Only very moderately infuscate ; the fore pair generally 

 lighter across the middle portion. 



Legs. — Pile, including the corbicular fringes, all dark. 



Dimetisiojis . — Length, 14 mm. to 15^ mm. ; spread of wings, 34 mm. 

 to 36 mm. ; width of abdomen at second segment, 7 mm. to 8| mm. 



This species has its closest relative in rufochictus, of which 

 it may indeed be only a subspecies. I have been unable to 

 separate it structurally from ridocinctus, but it may readily 

 be separated from that species, as it is known to me, by its 

 darker occiput and its much wider and better defined black 

 interalar band. The yellow pile of mexicensis is pale straw 

 yellow. The red pile is somewhat variable in shade, but, 

 when the shade is deepest, it is perhaps best described as 

 dark ferruginous. 



Psitliyrus fernaldae new species. 

 Psithyrus hisularis, Ashmead, Proc. Wash. Acad. Sci., IV, 1902, May 



23, p. 130 (pars). 

 Psithyrus insularis, Ashmead, Hym. of Alaska, 1904, p. 136 (pars). 



