32 PROCEEDINGS OF THE NATIONAL MUSEUM vor,. 82 



PSEN (MIMESA) UNICINCTUS (Cresson) 



Mimesa nnicincttis Cresson, Proc. Ent. Soc. Philadelphia, vol. 4, p 488, 1865. 

 (Male, not female.) 



This species shows a sexual color dimorphism, the male having 

 only the apex of the first tergite and all of the second red, while the 

 female has in addition the greater portion of the third also red. The 

 antennal flagellum of the males has only the apical 5 or 6 segments 

 distinctly yellow below, the pale color fading out about the middle, in 

 which character it closely resembles the male of hasirufus. The 

 petiole of the abdomen is, however, narrower and slightly longer 

 than in that species and is distinctly convex above and without a 

 sharp lateroventral edge so that the side is not distinctly sulcate. 

 The sculpture of the propodeum is also less coarse, the areas adjacent 

 to the enclosure being rather finely striate and almost without 

 reticulations. 



Length, 6-8 mm. 



The species was originally described from Colorado, and all the 

 specimens now available to me, including both sexes, are from that 

 State. 



PSEN (MIMESA) BASIRUFUS (Packard) 



Mimesa 'basirufa Packard, Proc. Ent. Soc. Philadelphia, vol. 6, p. 406, 1867. 



(Female.) 

 ? Mimesa neb7-ascensis Smith, Univ. Nebraska Studies, no. 8, p. 390, 1908. 



This species, as already noted, is very similar in the male sex to 

 unicinctics, but the female is more readily distinguished on the basis 

 of the apically widened and dorsally flattened petiole of the abdo- 

 men, which is usually depressed in center above and occasionally has 

 a slight central sulcus or channel on almost the entire length. In 

 the only female of unicinotus I have seen the first tergite of the abdo- 

 men is broadly blackened on disk, while in all the females of hasi- 

 Tufus I have, this tergite is entirely red, as is also the extreme apex 

 of the petiole below. 



Length, 7-9 mm. 



Described from Maine and subsequently recorded from Washing- 

 ton, Oregon, Nevada, Arizona, Colorado, Montana, and British Co- 

 lumbia. I have seen it from Maine, New Mexico, South Dakota, 

 Colorado, and British Columbia. 



PSEN (MIMESA) PROXIMUS (Cresson) 

 Plate 1, Figure 19 



Mimesa proxima Cresson, Proc. Ent. Soc. Philadelphia, vol. 4, p. 488, 1865. 

 (Female.) 



This species is another in which the petiole of the abdomen is much 

 shorter than the hind femur. The dorsal surface of the petiole has 



