238 U. S. NATIONAL MUSEUM BULLETIN 209 



tropic Irenangelus, and the worldwide Ceropales. A number of 

 features distinguish Ceropales from the other Holarctic Psammo- 

 charidae, and for this reason there has been a tendency to differentiate 

 this genus sharply from the rest of the family, sometimes even to con- 

 sider it as a separate family. However, it seems certain that Xan- 

 thampulex and Irenangelus are very close to Ceropales, and if the 

 characters of this natural group of genera is considered, rather than of 

 Ceropales alone, there seems less justification for the traditional 

 separation. The widespread opinion that the male genitalia of 

 Ceropales are distinctive enough to justify family rank shows lack of 

 familiarity with the range of variation of these structures within 

 Ceropales and of the conditions in Xanthampulex and Irenangelus. 



The members of the Ceropalini are social parasites on other psam- 

 mocharids. The female parasite oviposits into a book lung of the 

 spider prey of the host, while it is left unguarded for a moment some 

 time after capture. After the spider is placed in a nest by the host, 

 the ceropaline egg hatches, and the resulting larva consumes the host 

 egg and then the spider. The female parasites have sometimes been 

 seen trailing females of prospective hosts, to be on hand when a spider 

 is captured. 



Genus Ceropales Latreille 



Ceropales Latreille, 1796, Precis des caracteres g6n6riques des insectes disposes 



dans un ordre naturel, p. 123. Type: Evania maculata Fabricius; designated 



by Curtis, 1839. 

 Ceratopales Schulz, 1906, Spolia hymenopterologica, p. 174 (emendation). 

 Agenioxenus Ashraead, 1902, Canadian Ent., vol. 34, p. 137. Type: (Ceropales 



rufiventris Walsh) = robinsonii Cresson; original designation. 

 Hypsiceraeus Morice and Durant, 1915, Trans. Ent. Soc. London, pp. 403, 405. 



Type: Evania maculata Fabricius; original designation. 



This is the only genus of the Ceropalini occurring in the Nearctic 

 region. It may be distinguished from nearly all other psammo- 

 charid genera by the fact that the hind tarsal claws are bent at the 

 middle in a sharp right angle. 



The Western Hemisphere species of Ceropales divide easily into 

 four species groups as indicated in the keys and descriptions below. 

 Very few Eastern Hemisphere species have been available for study 

 but it seems that most of them belong in groups different from those 

 defined for our fauna. 



Key to the Nearctic species of Ceropales 



1. Both claws of middle tarsus and hind claw of fore tarsus with a short erect 

 acute subapical tooth, or, in males of the fulvipes group, these claws 

 specialized and unlike one another and the second segment of the middle 



tarsus not distinctly longer than wide 2 



Both claws of middle tarsus and hind claw of fore tarsus with a long, ap- 

 pressed, obliquely truncate tooth; second segment of middle tarsus dis- 

 tinctly longer than wide 9 



