6 AMERICAN HYMENOPTERA. 



of flagelliiru more than one-third longer than the second ; scape concave beneath, 

 about as long as first joint of flagellum ; dorsiilum with strong, separated punc- 

 tures, those on the mesopleurse finer and closer and mingle with fine strife; mid- 

 dle segment with a large triangular basal enclosure, which is drawn-out almost 

 to apex, and bears oblique and transverse coarse folds, remainder of middle seg- 

 ment rugoso-reticulate, but more finely than usual, on the sides coarsely striated ; 

 legs brownish, tarsi testaceous, calcaria yellowish, tibiaj tolerably spinose ; abdo- 

 men elongate, shining, petiole rather slender, longer than hind femora, trisulcate 

 above, pygidium indistinctly raised down middle, with large punctures; wings 

 subhyaline, iridescent, nervures dark : head and thorax with pale fuscous pubes- 

 cence, that on legs silvery; abdomen with silvery pile; flagellum pale beneath. 

 Length 8 mm. 



'^.—Resembles the 9 ; antennse elongate, slender; first joint of flagellum 

 hardly one-tliird longer than second; scape stout; thorax perhaps a little more 

 finely sculptured than in the 9 ; legs scarcely spinose; petiole of abdomen about 

 as long as hind femora; flagellum pale beneath. Length 7 mm. 



Arizona. Two specimens. A slenderer insect than P. niger. 



4. Psen niger Pack. 



Psen nicier Packard, Proc. Ent. Soc. Phil, vi, 399, 9 (excl. % ), 1867. 



9. — Head less strongly punctured than in cylindricus, without any trace of 

 striae; face and clypeus with short, sparse, silvery pubescence and grayish pile, 

 the clypeus distinctly bidentate ; space between hind ocelli about one-third less 

 than that between them and eyes; dorsulum with strong, separated punctures, 

 those on the mesopleuraj extremely feeble, in fact the mesopleurte are nearly 

 smooth, except basally and apically ; triangular basal enclosure of middle seg- 

 ment not very large, and scarcely drawn-out aj)ically, containing a smaller trian- 

 gular smooth enclosure in the middle, on each side of which there are strong 

 folds ; the posterior surface of the middle segment iscoarsely rugoso-punctate, more 

 so than in ctjlhulncm, and is concave, on the sides with coarse folds or strise ; ab- 

 domen elongato-ovate, petiole robust, about as long as hind femora, strongly 

 trisulcate above ; mesopleurae beneath with silvery pile. Length 8 mm. 



% . — Head more closely punctured, especially on front; face and clypeus with 

 dense silvery pubescence; space between hind ocelli equal to about half of that 

 between them and eyes ; antennfe (flagella missing) ; thorax with dorsulum rather 

 finely and closely punctured ; middle segment very coarsely rugose, the basal 

 enclosure larger; petiole longer than hind femora. Length 8 mm. 



Virginia ; Canada. The silvery pubescence of front and clypeus 

 is much sparser than in cijlindricus or regidaris. Packard had con- 

 fused the sexes of two species under niger, and I have retained as 

 niger that which, in my opinion, best befits the name. 



5. Psen regularis n. sp. 



9 . — Head stronglj^ and distinctly punctured, closely on front ; face and clypeus 

 with dense, rather long, silvery pubescence, the clypeus not or indistinctly biden- 

 tate; space between hind ocelli more than one-third less than that between them 

 and eyes; antennte (flagella missing); punctures of dorsulum stronger than in 

 niger; enclosure of middle segment larger than in niger, with a similar central 

 smooth enclosure, on each side of which the folds are stronger and more obvious ; 



