346 AMERICAN HYMENOPTERA. 



Thorax. — Dorsum, mesopleurato bases of legs, metapleura and sides 

 of median segment covered with yellow pile. 



Abdomen. — Dorsum : segments one, two and three entirely covered 

 up with yellow pile ; segment four usually entirely black, but some- 

 times partly or even wholly yellow ; segment five usually entirely black, 

 but sometimes entirely yellow ; segment six usually entirely black, but 

 sometimes yellow ; segment seven usually mostly dark, but always 

 with some light pile and sometimes entirely covered with it. Venter 

 clothed for the most part, except often the apical segments more or 

 less dark, with light pile. 



Genitalia. — Outer spatha (fig. 140) very short and broad, its ante- 

 rior margin deeply and evenly incurved, side margins rather evenly 

 rounded behind and incurved in front, posterior margin straight or 

 incurved ; apical border of ventral surface bearing short hairs all the 

 way across and with a somewhat scattering tuft of long hairs on each 

 side ; anterior lateral projections long and rounded at the end. Inner 

 spatha (fig. 145) with side margins strongly incurved ; apex squarish 

 with corners more or less pointed, the posterior margin usually being 

 incurved somewhat ; ventral surface of apical portion covered with 

 short to moderately long hairs ; a single, large, median fenestra pres- 

 ent somewhat in front of the center. Claspers (figs. 69 and 76) with 

 branches strongly pointed on the inner sides of their tips as seen from 

 above ; volsellae much broader than those of B. vagans ; tips of the 

 nuces protruding prominently at the bases of the volsellae, this being 

 the most distinctive character exhibited by the genitalia ; sagittae as 

 already described for the group. 



Wings. — Subhyaline ; much lighter than those of queens. 



Legs. — Coxae, trochanters and femora all with considerable light 

 pile ; fore and middle tibiae usually entirely dark, but sometimes with 

 considerable light yellowish ferruginous pile on their hind sides, espe- 

 cially toward the tips ; outer faces of posterior tibiae very slightly 

 convex and nearly naked down the middle, but with a scattering of 

 short hairs; corbiculae rather weak, their fringes mostly black, but 

 usually, at least the hind ones, with more or less of a dull ferruginous 

 tinge ; posterior metatarsi with hind fringes short. 



Dimensions. — Length: queen, 15 mm. to 20 mm.; worker, 9 mm. 

 to 14 mm. ; male, 11 mm. to 15 mm. Spread of wings: queen, 34 

 mm. to 41 mm. ; worker, 21 mm. to 31 mm. ; male, 25 mm. to 30 

 mm. Width of abdomen at second segment : queen, 9 mm. to 11 

 mm. ; worker, 5 mm. to 8 mm. ; male, 5 mm. to 6^ mm. 



Described from a large series of specimens of each sex. 

 Variations. — Besides the variations noted in the above de- 

 scription, the following are worthy of notice : 



Color Variant 1. — Very rarely the queen has the pleura covered with 



