358 U. S. NATIONAL MUSEUM BULLETIN 216 pabt 3 



11. Trychosis albitarsis (Cresson) 



Figure 391 



Front wing 5.7 to 8.2 mm. long; punctures on head, thorax, and 

 legs exceptionally small and dense; clypeus large, closely punctured, 

 very strongly convex, its apical margin moderately arcuate; temple 

 weakly convex; cheek long, with strong crowded punctures and 

 usually with some short horizontal wrinlding, near the occipital 

 carina the wrinkles often making strong rugae; occipital carina sharp, 

 high, its lower part often forming a lamella that may be as high as 

 the width of third segment of maxillary palpus; second segment of 

 flagellum about 2.5 as long as wide in male, about 3.2 as long as 

 wide in female; thorax stout; notaulus distinct or indistinct, extending 

 about 0.25 the length of mesoscutum; punctm^es on mesopleurum 

 small, sharp, mostly adjacent; propodeum moderately short, its 

 apical carina forming a short, weak sublateral crest, angled forward 

 a little between the crests but more nearly horizontal than usual, 

 the median part weak or sometimes absent; hind femur about 5.4 

 as long as deep in male, about 5.1 as long as deep in female; sides 

 of areolet weakly convergent or subparallel; nervulus beyond basal 

 vein by about 0.45 its length; nervellus broken near its lower 0.45; 

 petiole rather wide, with a distinct ventrolateral longitudinal carina 

 and dorsolateral longitudinal ridge, its lateral face with fine but 

 rather strong, irregularly vertical wrinlding; first sternite with fine, 

 irregular, longitudinal wrinkling, its apical 0.45 ± bordered laterally 

 by a carina that represents the lower edge of first tergite (this carina 

 shorter or absent in all other species except T.fuscata); second tergite 

 subpolished, with short, exceptionally dense hairs (denser in female 

 than in male), the sockets of which are separated by about 0.65 the 

 length of the hairs; nodus of ovipositor unusually weak; ovipositor 

 sheath about 0.24 as long as front wdng. 



The small, dense punctures on the head, body, and legs, longitudi- 

 nally wrinlded first sternite of which the apical 0.45 ± is bordered 

 laterally by a carina, and ferruginous second and third tergites are 

 distinctive. The character of the wrinlded and bordered fu'st sternite 

 occurs also in T. fuscata, but in that species the second and third 

 tergites are blackish. The species semirubra and latidens tend to 

 have the first sternite wrinlded and bordered, but not as definitely 

 as in albitarsis ondfuscata. 



There is an eastern and a western subspecies, as keyed and de- 

 scribed below : 



1. Apical 0.4 or less of male hind basitarsus whitish; female flagellum without a 

 median white band; range: Rocky Movintains to Pacific Ocean. 



11a. albitarsis peratra, new subspecies 



