IV CONTENTS 



Subfamily Gelinae — Continued 



Tribe Mesostenini — Continued Page 



3. Subtribe Nematopodiina 461 



Key to the Nearctic genera of Nematopodiina 462 



1. Genus Messatoporus 462 



2. Genus Acroricnus 468 



4. Subtribe Echthrina 476 



Key to the Nearctic genera of Echthrina 477 



1. Genus Xylophrurus 478 



2. Genus Echthrus 486 



3. Genus Agonocryptus 502 



4. Genus Cryptohelcostizus 504 



5. Genus Helocostizus 513 



5. Subtribe Sphecophagina 522 



1. Genus Sphecophaga 523 



Figures 530 



Indices 569 



