34 U. S. NATIONAL MUSEUM BULLETIN 216 



4. Genus Trieces 



Figure 165,b 



Trieces Townes, 1946, Bol. Ent. Venezolana, vol. 5, p. 60. Type: Exochus tex- 

 anus Cresson; original designation. 



Front wing 3 to 6 mm. long; front spur of middle tibia 0.25 to 0.65 

 as long as hind spur; thorax with an exceptionally streamlined appear- 

 ance; pronotum evenly convex as the upper margin is approached, 

 without an impression paralleling its upper margin ; mesopleural suture 

 indistinct or absent; metapleurum bare or with hairs in its upper 

 part, with more or less distinct wrinkles near attachment of hind 

 coxa; lateral carina of first tergite often weak or obsolescent; second 

 tergite with a median and a sublateral longitudinal carina extending 

 its entire length; third tergite with a median carina and sublateral 

 carina, the sublateral carina extending 0.3 or more of the tergite's 

 length; fourth tergite basally sometimes with median and sublateral 

 carinae but usually ecarinate. In Trieces teres the carinae on the 

 tergites are reduced. See the description of that species. In all other 

 respects this genus is similar to Chorinoeus. 



This is a large genus of probably worldwide distribution. The 

 species, however, are scarce in collections. Most of them occur 

 sparingly, among shrubby growth in rather dry habitats. When 

 collected they have a habit of folding their wings and antennae back 

 and pushing themselves along rather than crawling. This makes 

 them adept at squeezing through the meshes of an insect net. 



Key to the Ne arctic species of Trieces 



1. Median and sublateral longitudinal carinae of third tergite reaching its apex 



and continued on to the fourth tergite. Dentatus group 2 



Median and sublateral longitudinal carinae of third tergite present on its 

 basal 0.8 or less (or in T. teres, hardly indicated at all), completely absent 

 from fourth tergite except in some males of T. costatus 3 



2. Lateral carina of scutellum not projecting beyond apex of scutellum; pre- 



pectal carina complete, dorsally reaching front edge of mesopleurum; 

 metapleurum without hairs (fig. 182, b); hind femur blackish. 



18. calvatus, new species 



Lateral carina of scutellum projecting beyond apex of scutellum to form an 



acute tooth; prepectal carina incomplete above, not reaching front edge of 



mesopleurum; metapleurum with numerous hairs along its upper margin 



(fig. 182, c); hind femur fulvous 19. dentatus, new species 



3. Metapleurum with a vertical, slotlike pit in its hind end, broadly hairy along 



its entire upper margin (fig. 182, d) ; face 1.5 to 2.1 as wide as high. Onitis 



group 4 



Metapleurum without a pit in its hind end, not broadly hairy along its entire 

 upper margin, if with hairs along its upper margin they are in a band that 

 is either narrow or incomplete (figs. 180,a to 182, a); face 1.0 to 1.5 as wide 

 as high 6 



