192 



AMERICAN HYMENOPTERA. 



TA, tibia. 



tc, transverse cubital vein. 



tcl, first transverse cubital vein. 



tc2, second transverse cubital vein. 



tc3, third transverse cubital vein. 



tg, tegula. 



tm, transverse median vein. 



tr, trachea. 



U, uncus. 



V, volsella or lacinia. 



ver, vertex. 



W, median segment. 



X, membrane of squama. 



Y, shaft of sagitta. 



1-6, abdominal plates. 



Explanation of Plates. 



The figures on plates two to four inclusive and figure 53 

 on Plate VIII were prepared, by tracing, from photographs. 

 All the other figures, except those on Plate I, are camera 

 lucida drawings. The plates are all by the author, except 

 XIX and XXI, which were prepared by Miss Iris L. Wood 

 of St. Anthony Park, Minnesota, from outlines made by the 

 author. 



PLATE I. 



Outer view of right poste- 



FlG. 



Outer view of right 



Fig. 



A. — Psithyrus laboriosus (Fabricius). 

 rior tibia of female. x5. 



B. — Bombus {Bonibias) fraiernus (Smith), 

 posterior tibia of queen. x5. 



C. — Bombus impatiens (Cresson). Ventro-lateral view of abdo- 

 men of queen. x5. 



D. — Bombus {Bombias) fraternus (Smith). Front view of head 

 of queen. x5. 



E. — Bombus pemisylvanicus (Deeger). Front view of head of 

 queen. x5. 



F. — Bombus pennsylvanicus, front view of head of male. x5. 



G. — Bombus {Bombias) auricomus Robertson. Front view of 

 head of male. x5. 



H. — Psithyrus /atitarsus'M.orrxW. Ventro-lateral view of abdomen 

 of female. x5. 



I. — Psithyrus laboriosus. View of outer side of right posterior 

 metatarsus of female. x5. 



K. — Bombus affinis Cresson. View of outer side of right poste- 

 rior metatarsus of queen. x5. 



PLATE n. 

 1. — Bombus impatiens^ side view of body of queen. x5. 

 2. — Bombus impatiens, dorsal aspect of thorax of queen. 



