216 NEOTROPICAL PSELAPHIDAE 



tarsal claws. Sharp (1887) and Raff ray (1890) followed this lead, describing 

 their new species in subgenus Arthmius of Batrisus. 



In 1897 Raffray, in an important paper, reaffirmed his earlier belief 

 of 1894, that Arthmius of LeConte was suflBciently distinct to warrant 

 generaic status, and divided the genus into three subgenera: Syrbatus Reitter, 

 Arthmius ss. of LeConte, and Syrmocerus Raffray. These three subgenera 

 are now recognized as distinct genera, and as such are treated separately in 

 this paper as I have been unable to find species which intergrade in their 

 pronotal anatomy to allow bridging the gap between one genus and another, 

 although all three show an arthmioid habitus. 



The neotropical batrisines become numerically important by virtue of 

 Arthmius. Although the genotype is nearctic, the genus as a whole is over- 

 whelmingly neotropical. At present there are five species known north of 

 Mexico, of which four are distributed east of the Rocky Mountains and one 

 from Oak Creek Canyon, Arizona, at 6000 feet [morsus Fletcher, 1932). In 

 contrast the neotropics have at present 94 species distributed: Mexico (12), 

 Guatemala (3), Panama (2), Canal Zone (1), Colombia (5), Venezuela (2), 

 Bolivia (10), Peru (5), Chili (1), Paraguay (2) and Brazil (51). Brazil, 

 especially the drainage basin of the Amazon river, would seem to be the 

 center of taxonomic diversity, and many new species remain to be discovered 

 before our information can be considered complete enough for any generalized 

 statement. At present I am inclined to view Arthmius as a typical neotropical 

 genus of the rain forest, spreading with difficulty into drier or cooler areas. I 

 should be surprised if species of the genus were found north of the deciduous 

 forest biome or above the deciduous forest montane zone. 



Their sharp mandibles presuppose an adherence to the predaceous family 

 habit, and they do not appear to have adjusted to a life with ants and termites. 

 Their natural habitat is the forest floor mold. New evidence presented later 

 seems to prove that they inhabit this stratum by day and fly by night. Their 

 large eyes and long wings support this view. 



Sex is readily ascertained. The males have six stemites fully visible (not 

 counting the morphological first sternite) , of which the last is quite minute as 

 a rule, placed as an ovate-transverse plate between the very large last tergite 

 and next to the last sternite. This fifth visible sternite is usually large and 

 variously ornamented or formed. The antennae, legs, and especially the dorsal 

 surface of the head may be highly abnormal. 



The females have simple legs, antennae, and head as a rule and always 

 only five stemites fully visible (not counting the morphological first sternite), 

 of which the last is large. 



I have attempted to key out the species of Arthmius. This would have 

 been impossible but for the work of Raffray since the types are not at hand in 

 most instances. In 1897 Raffray keyed out the species of the genus then known, 

 and this was especially good since he had direct access to most of the types 

 of the early species of Schaufuss, Sharp, and Reitter. In the following keys 

 this 1897 background is integrated with the more recent work. 



