40 U. S. NATIONAL MUSEUM BULLETIN 209 



This species occurs from Panamfi to the Big Bend country of 

 Texas. The collection of three females at light at Cau-o, Costa Rica 

 is of interest, as it is another case of a species with enlarged ocelli 

 coming to lights at night. 



Genus Priocnessus Banks 



Priocnessus Banks, 1925. Bull. Mus. Comp. Zool., vol. 47, p. 337. Type: Salius 



neotropicalis Cameron; designated by Pate, 1946. 

 Cressochilus Banks, 1941. Canadian Ent., vol. 73, pp. 119, 120. Type: Pompilus 



nuperus Cresson; original designation. 

 Amerocnemis Banks, 1945. Bol. Ent. Venezolana, vol. 4, p. 93. Type: Ameroc- 



nemis hequaerti Banks; original designation. 



Medium sized to moderately large species, of rather slender build, 

 the forewing in Nearctic species 6.5 to 17 mm. long; clypeus very 

 large, convex, in some males with a highly modified shape; pronotum 

 short, its hind margin arcuate; second intercubital vein somewhat 

 curved; second recurrent vein reaching second cubital cell at or just 

 beyond its middle; cubital vein fading out before reaching the wing 

 margin; base of first discoidal cell with a faint subcircular irregularity 

 in its membrane; nervulus beyond the basal vein by 0.3 to 1.2 its 

 length; nervellus ending at or beyond juncture of cubitella with 

 discoidella; anal lobe about 0.7 to 0.8 as long as submediella (pi. 1, 

 fig. 4); hind tibia with a strong dorsal serration; brush on inner side 

 of hind tibia of moderate width, without a subapical constriction; 

 last tarsal segment without or with a few preapical bristles beneath; 

 tooth on tarsal claw of female erect and acute, that on tarsal claw 

 of male usually more or less modified, sometimes in the form of a 

 subbasal lobe. 



Priocnessus is a typical case of a Neotropic genus with intrusions 

 into the southern portions of the Nearctic region. No species are 

 known from the Eastern Hemisphere. The described Neotropic 

 species known to me are Pompilus (Priocnemis) cincticornis Cresson 

 1867, Salius {Priocnemis) neotropicalis Cameron 1891, Priocnemella 

 monticola Banks 1938, Priocnessus prominens Banks 1945, Ameroc- 

 nemis bequaerfi Banks 1945, and Priophanes ornata Banks 1945. The 

 last species has not previously been referred to Priocnessus. The 

 genus is much larger in the Neotropics than this small number of 

 described species might indicate. There are six Nearctic species. 



Key to the Nearctic species of Priocnessus 



1. Head and body rufous or mostly rufous 2 



Head and body black 4 



2. Forewing subhyaline, with three brown cross-bands (pi. 2, fig. 16). 



4. apache (Banks) 

 Forewing uniformly dark brown 3 



