PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



Issued |i|$fv vl 0?M ^y '^* 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol. 106 Washington: 1956 No. 3367 



THE NEARCTIC SPECIES OF TRIGONALID WASPS 



By Henry Townes » 



The Trigonalidae is a small family of Hymenoptera, of which only 

 four species belonging to four genera are known in the Nearctic Region. 

 All of them are parasites, usually secondary parasites, and their hosts 

 include Vespidae, Pergidae, and dipterous and hymenopterous para- 

 sites of caterpillars. 



Adult trigonalids look somewhat like medium-sized sawflies or wasps. 

 The relationships of the family appear to be with the Aculeata and it 

 fits best in the Chrysidoidea (including the Bethyloidea), but it is 

 aberrant wherever placed and the natural relationships of the families 

 of Apocrita will have to receive a general study before the proper 

 position of this family can be stated with confidence. Characters by 

 which trigonalids may be distinguished from other families of Apocrita 

 are: Flagellum with 14 to more than 20 segments; costal cell of fore- 

 wing present; hindwing with distinct venation and two closed cells; 

 anal lobe represented by a small vestige; and legs usually with two but 

 sometimes with one trochanter each. Figure l,a illustrates a typical 

 member of the family. 



' Research Associate, University of Michigan, Ann Arbor, Mich. 



295 



