14 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



head height; labella rather small; palpi black. Thorax with the 

 usual three broad black vittae extending as far as scutellum, the latter 

 shining black, without vittae. Abdomen black, with the last three 

 segments tliinly gray pollinose, often to their apices; intermediate 

 segments each with three large black spots; strong median marginal 

 bristles on the first two segments, marginal rows of about eight on the 

 last two. Genital segments black; inner forceps (pi. 3, fig. 13) curved 

 forward, tips laterally compressed; outer forceps yellow, tapering to 

 points round in cross section, more slender than inner forceps; penis 

 with black, heavily chitinized hood, bootlike in appearance, with the 

 toe of the "boot" pointed towards the inner forceps and with a trans- 

 parent keel on its posterior border; anterior clasper slightly more than 

 half as long as penis, tapering to a stout, anteriorly directed point. 

 Wings with two to three small hairs at base of third vein. Legs 

 black; hind tibia with a complete row of uneven bristles on the 

 outside surface. 



Female. — Not distinguished with certainty from females of P. dis- 

 tortus. The front at narrowest, in five specimens averaged 0.18 of 

 the head width (measurements as follows: 0.15, 0.16, 0.17, 0.22, 0.22). 

 Usual sexual differences in genitalia and in length of claws and 

 pulvilli. Otherwise like the male. 



Length, 6 to 7 mm. 



Redescribed from the following males : One from Holyoke, Massa- 

 chusetts, no. 1478c Dimmock's Ent. Notes; three from Washington. 

 District of Columbia, one labeled "from wasp's nest" (H. G. Dyer) ; 

 one labeled "from butter wasp" (C. V. Riley); four from Lafayette, 

 Indiana (J. M. Aldrich) ; two from Tennessee Pass, Colo. (J. M. 

 Aldrich); three from White Mountains, New Mexico, two labeled 

 "flowers of Cicuta occidentalism' and the other "flowers of Solidago 

 trinervata" (C. H. T. Townsond); two from Mono Lake, California 

 (J. M. Aldrich); two from Sierra Madra, Chihuahua, Mex. (C. H. T. 

 Townsend); all in the collection of the National Museum. One 

 from Sugar Grove, Ohio, and another from Columbus, Ohio, labeled 

 "parasite of Trypoxylon politum,'' both in collection of Prof. J. S. 

 Hine. One male, Macerat, Italy (?), determined by Professor Bezzi, 

 and one male, Rambouillet, France. Both European specimens in 

 which the genitalia was relaxed were found to be identical with North 

 American material. 



Owing to tlie inclusion of two distinct species under the name 

 signatus, published records referring to this species up to the present 

 should not be accepted without verification. P. signatus occurs in 

 Europe and is also generally distributed over North America, having 

 been identifietl l)y the writer from males with tlie genitalia relaxed, 

 from Massachusetts, District of Columbia, Indiana, Colorado, New 

 Mexico, California, and Chihuahua, Mexico. It is attracted to 



