8 U. S. NATIONAL MUSEUM BULLETIN 216 



and an undescribed genus from the Orient belong to this group. 

 Alophosternum has been reared from leaf-mining larvae. 



Brachycentropsis group: Occipital carina absent above; meso- 

 scutum covered with dense hairs; tarsal claws of female each with a 

 basal tooth; propodeum behind with a large smooth area bordered by 

 a carina; first tergite with strong, complete lateral longitudinal carina, 

 its dorsal longitudinal carinae very short and weak ; female subgenital 

 plate heavily sclerotized; ovipositor relatively short, compressed, the 

 apex of its lower valve with a dorsal lobe that encloses apex of upper 

 valve. Brachycentropsis of the Mediterranean region is the only 

 genus. 



Camptotypus group: Occipital carina absent above, often entirely 

 absent; mesoscutum with few hairs or none, polished; tarsal claws of 

 female with a large basal tooth; male subgenital plate not elongate; 

 ovipositor straight. The genera of this group are tropical, Campto- 

 typus in the Old World tropics and Zonopimpla, Odontopimpla, and 

 four unnamed genera in the New World tropics. The host relations 

 are not well known. 



Perithous group: Occipital carina complete, without a median dip; 

 tarsal claws of female without a basal tooth; propodeum with its 

 petiolar area bounded by a more or less distinct carina (bounded in 

 a similar way in the Brachycentropsis group but in none of the others) ; 

 male subgenital plate elongate, ending in a median point. Perithous 

 is the only genus. It parasitizes the nests of aculeate Hymenoptera 

 living in stems. 



Key to the Nearctic genera of Pimplini 



1. Tarsal claws of female without a basal lobe (fig. 292,a); subgenital plate of 



male longer than wide, prolonged medially into a rounded point; abdomen 

 of the Nearctic species black with a narrow white apical band on each 



tergite 14. Perithous (p. 209) 



Tarsal claws of female with a large basal lobe (at least in the Nearctic species) ; 

 subgenital plate of male wider than long, usually without a median point; 

 abdomen usually entirely black, rarely colored as above 2 



2. Prepectal carina absent (fig. 291, b); occipital carina absent above; basal half 



of ovipositor down-curved (fig. 291, b) 13. Alophosternum (p. 206) 



Prepectal carina present except in Dolichomitus cuspidatus (figs. 285-291, a); 

 occipital carina nearly always present above; basal half of ovipositor 

 straight (figs. 285-291,a) 3 



3. Occipital carina not dipped downward at the midline, always strong medially; 



areolet often absent; frontal orbits often marked with white. (Parasites 



of spider eggs.) 4 



Occipital carina dipped downward at the midline, sometimes weak or rarely 

 obsolete medially; areolet present; frontal orbits never marked with 

 white 6 



4. Nervellus broken below the middle or not broken; ovipositor tapered, its 



apical half more or less upcurved (fig. 291, a); female subgenital plate large 

 and projecting (fig. 291, a) 12. Clistopyga (p. 195) 



