6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 82 



DIODONTUS SULCATUS, new species 



Female. — A larger species than trisidcus, and quite similar in struc- 

 ture, the distinctions consisting of those listed in the foregoing syn- 

 optic key. I had some doubt as to the propriety of accepting this 

 as h^lsulcus, the tj^pe specimen of which was not examined by Mr. 

 Rohwer, but I finally decided that the smaller and much more widely 

 distributed and common species already dealt with is more likely 

 to prove correctly identified as that species. There are some speci- 

 mens of trisulcus in which the carina between the bases of the anten- 

 nae has a slight sulcus on the anterior portion, but in such cases the 

 petiole of the abdomen has no ventral median carina and the propo- 

 deum is differently sculptured. 



The male is not known. 



Length, 7-7.5 mm. 



Type.—U.^.'^M. No. 44205, from Harrisburg, Pa., 1921 (Cham- 

 plain). Paratypes, topotypical — 1, by the same collector, July 11, 

 1921 ; 1, Wetzels Swamp, July 9, 1910 ; and 1, Carlisle, Pa., June 24, 

 1910, the last 2 taken by W. S. Fisher. 



Genus PSENULUS Kohl 



Psenulus Kohl, Ann. Naturh. Hofmus. Wieu, 1896, p. 293. 



I have examined the genotype, fuscipennis Dahlbom, and can find 

 no character other than one of the venation of the fore wing to justify 

 the separation from Diodontus. The second cubital cell receives both 

 recurrent nervures in Psenulus^ while it receives but one in Diodon- 

 tus as a general rule, though at times the first recurrent nervure may 

 be interstitial with the first transverse cubital. 



As the group is unrepresented in North America as far as is known 

 at present, it is not necessary to deal further with the matter of the 

 validity of the genus. 



Genus PSEN Latreille 



Psen Latreille Precis des caracteres g4n§riques des insectes, etc., p. 122, 



1796. (Genotype, Sphex atra Fabricius.) 

 Mimesa Shuckard, Essay on the indigenous fossorial Hymenoptera, p. 228, 1837. 



(Genotype, Mimesa equestris Wesmael.) 

 Dahlbomia Wissmann, Ent. Zeitung, vol. 10, p. 9, 1849. (Genotype, Sphex 



atra Fabricius.) 



There are several rather well marked segregates of this genus in 

 North America to which we give subgeneric status, all of them fall- 

 ing within the genus in its widest sense as limited in the generic 

 synopsis given herein. Following is a key for the separation of 

 these subgenera: 



