Tribe 6. Metopiini 



This tribe was isolated by Raffray (1904, p. 106) to contain pselaphids 

 having the following combination of characters: (1) head with antennae 

 contiguous or subcontiguous, articulated on a prominent median antenna! 

 tubercle, the head constricted behind the tubercle and then expanded poster- 

 iorly; (2) eleven-segmented, long, slender antennae which are always con- 

 spicuously geniculate (PL XVIII) as a consequence of the inordinately long 

 first segment; (3) mentum normal, not expanded to cover the mouth and 

 mouth-parts; (4) first sternite small but visible between the posterior coxae 

 as a plate which is not longer than these coxae; (5) medial faces of posterior 

 coxae, articulating with the trochanters, subtriangular to subglobular; (6) 

 intermediate trochanters short, very obliquely articulated with the femora so 

 that the latter are near their respective coxae; (7) three-segmented tarsi hav- 

 ing the first segment short and the last two long, the last segment bearing 

 two very unequal tarsal claws. 



Few tribes have such a characteristic facies. Their long, slender legs, long 

 and geniculate antennae, and contiguous antennal insertion make a picture 

 seldom forgotten. Within the neotropics the only pselaphids they remotely re- 

 semble are Goniacerini, also with a strong antennal tubercle and geniculated 

 antennae [Bibrax) , but with the first sternite very long, clearly visible from 

 side to side and longer than the posterior coxae. 



Sex in Metopiini can be quickly and infallibly diagnosed: the females 

 have six sternites; the males have seven stemites, of which the seventh is in 

 two plates, a right and a left as in the males of some euplectine genera. As 

 in these latter, these two subtriangular valves move laterally at copulation, 

 to allow extrusion of the penis; in repose, these plates meet medianly to form 

 a median, longitudinal carina or sulcus with carinated edges. 



The Metopiini are exclusively neotropical, centering in the rain forest of 

 the Amazon River basin. From here the species extend with decreasing fre- 

 quency south into Argentina and north to Panama. They are apparently 

 nocturnal, spending the day beneath bark of fallen logs or leaf mold of forest 

 floors, and flying at dusk. Some come to lights at night. Many species live 

 with ants. One of the new species has been found with termites. 



The following key to genera has been modified from Raffray, 1908. 



Key to the Geneea 



Each side of pronotum bearing a long spine (PI. XVIII) 



METOPIOXYS 



Sides of pronotum not spinose (PI. XVIII) 2 



2. Third antennal segment subequal to the second segment in length, 



or very much longer METOPIAS 



(204) 



