AMERICAN HYMENOPTERA. 2oO 



% . Body stout, violaceous. Autennfe black, long, third and fourth 

 joints equal, apical joint slender and as long as the preceding; head 

 and pleura granulated ; thorax above coarsely punctured ; tergum and 

 legs smooth and shining, tibiae pilose, nasus with a deep and angular 

 notch, tarsi stout, densely covered with black setaceous hair; inner 

 claw tooth obtuse, removed from the tip ; wings violaceous subhyaline, 

 stigma and costa black. 



Xew England, ]Middle States, Md., Mo. Common. 



2. D. arvensis. 



Dolen'.s arvensis. Say. Long's Second Exp. II, 1824, .319, 2, 9- 

 Dosi/theus arvensis, Norton, Bost. Proc. viii, 151, 1. 

 Blue-black; the prothorax and mesothorax rufous, with a black vitta on an- 

 terior lobe. Length 0.32.— 0.36. Br. wings 0.66—0.74 inch. 



$ . Kather long and stout, color violaceous ; antennae black, third 

 joint longer than fourth, apical joint shorter and moi'e slender than the 

 preceding; head and body punctured as in D. unicolor ; a yellowish 

 rufous spot covers the prothorax and mesothorax ; a vitta on the ante- 

 rior lobe of mesothorax black ; scutel violaceous ; legs the color of 

 body ; formed as in D. unicolor. Wings subviolaceous, nervures black. 

 Yar. a. The vitta on the mesothorax extends across the side lobes, 

 forming a three-lobed spot. 



New England, Middle States, Fla., Mo. Very common. 

 Taken in April, on willows. No males. The ground color is pre- 

 cisely the same with that of D. unicolor^ of which no females have yet 

 been taken. The formation of the tarsi is also similar, being shorter 

 than in the following species, and the apical joint shorter. 



3. D. sericeus. 



Dolerus sericeus, Say, Long's Second Exp. II, 1824, 320, 3, 'J, 9 • 

 Norton, Bost. Proc. viii, 151, 1. 

 "Entirely black, immaculate." Length 0.32—0.40. Br. wings 0.64—0.80 inch. 



% . Body long and rather slender, color shining black ; antennae 

 long, third joint rather longer than fourth, final joint but little shorter 

 than the preceding ; abdomen rather longer than in D. iinicolor and 

 more rounded at the apex ; rather more of white hair upon the face 

 and legs; posterior tibiae at tip stout; tarsi long and slender, less pi- 

 lose, apical joint long ; inner claw tooth obtuse ; wings subviolaceous, 

 nervures black. 



9 . The female is larger and the abdomen stouter ; antennae shorter, 

 not extending beyond base of abdomen, third joint longer than fourth. 



The males are very abundant, the females rare. 



A single specimen {%^ from Massachusetts, in the Collection of the 

 American Entomological Society, has four submarginal wing-cells, the 



