438 U. S. NATIONAL MUSEUM BULLETIN 216 



There are four genera of this tribe, all of which occur in our area. 

 Their larvae parasitize coleopterous borers in dead wood and the 

 adults may be collected on dead tree trunks or in forests where there 

 is dead wood. 



The revision of the genus Aplomerus (below) is a separate contri- 

 bution under the joint authorship of Henry Townes and George 

 Townes, published as part of this monograph for the convenience of 

 having all members of the subfamily treated in one place. 



Key to the genera of Xoridini 



1. Mandible without two teeth, its apex chisel-shaped; epomia long and strong, 



usually projecting dorsally as a tooth; female antenna curved or elbowed 

 subapically, at the curve or elbow with one, two, or a series of peglike setae. 



Worldwide 4. Xorides (p. 489) 



Mandible with two subequal teeth (as normal) ; epomia absent or short and 

 weak, not projecting dorsally; female antenna not specialized subapically 

 (as described above) 2 



2. Hind femur with a strong median ventral tooth. Holarctic. 



3. Odontocolon (p. 448) 

 Hind femur without a median ventral tooth 3 



3. Frons with a strong median horn or tubercle; body subcylindric. Holarctic. 



1. Ischnoceros (p. 438) 

 Frons without a median horn or tubercle; body flattened. Nearctic. 



2. Aplomerus (p. 439) 



1. Genus Ischnoceros 



Figure 304,b 



Ischnoceros Gravenhorst, 1829, Ichneumonologia europaea, vol. 2, p. 949. Type: 

 Ichneumon rusticus Fourcro} 7 ; designated by Viereck, 1914. 



Head and body not depressed; apex of mandible with two subequal 

 teeth ; frons with a strong median horn or tubercle that is often hol- 

 lowed out above ; female flagellum not specialized as in Xorides ; epomia 

 absent; hind femur not thickened, without a tooth beneath; first ab- 

 dominal segment short, stout, rather strongly bent at the middle ; second 

 tergite with weak oblique basal grooves; second and third tergites 

 punctate or transversely aciculate; apical part of ovipositor weakly 

 compressed, the ventral valve with about five ridges, basad of which 

 there is no roughened area. 



There are several Palaearctic species and one in the United States. 



1. Ischnoceros clivulus Townes 



Ischnoceros clivulus Townes, 1957, Proc. Ent. Soc. Washington, vol. 59, p. 21; 9 • 

 Type: 9 , Cinder Cone, Lassen National Park, Calif. (Berkeley). 



Male: Unknown. 



Female: Front wing 7 to 8 mm. long; frons with rather fine punc- 

 tures and a large, median, moundlike, weakly compressed tubercle 



