370 NEOTROPICAL P3ELAPHIDAE 



dispersal highway between Central and South America, and although it has 

 about forty miles of shore-line, contains but six odd square miles of surface. 

 About half of this area is in relatively untouched rain forest, and the island 

 houses the Institute for Research in Tropical America. The climate, flora, fauna, 

 ecology have been often and well studied (Allee, 1926, 1926a; Carpenter, 1934; 

 Chapman, 1929; Dunn, 1931; Enders, 1935; Gross, 1930; Kenoyer, 1929; Park, 

 1938; Park, Barden and WilHams, 1940; Rau, 1933; Schneirla, 1938; Standley, 

 1927, will serve to open the bibliography for those unfamiliar with work done 

 on the region) . 



Now Barro Colorado Island has been subjected to two summers of collect- 

 ing Pselaphidae by the author, and in addition I have worked over the forest 

 floor and termitophilous pselaphids of Dr. Alfred Emerson and Dr. Laura Hare 

 from this forest, as well as the pselaphids obtained by quadrat and Berlese 

 sample of Dr. EHot Williams on the island forest floor; finally Dr. Bradley col- 

 lected here and these pselaphids have been described by Fletcher (1927) . I men- 

 tion this in detail as the point is important. That is, the pselaphid fauna of this 

 six square miles may be said to be fairly well known, and thus will serve as a 

 guide to taxonomic density. I have little doubt that many other species await 

 discovery here, but there are at present forty-five species of Pselaphidae known 

 from the island. Therefore the taxonomic density of Barro Colorado Island is 

 about 1 species per one-tenth square mile. 



When this ratio of 1 : 0.12 is contrasted with the densities in Table IX, 

 the gaps in our knowledge are better appreciated. A density of less than 

 1 : 10,000 in Pselaphidae represents practically unexplored territory, and hence 

 Peru, Uruguay, British Guiana, and Ecuador are areas where collections are 

 desirable. 



Having the Barro Colorado Island figures to use as a basis for estimation, 

 some effort should be made to give a speculative figure of the actual (described 

 and undescribed) number of species of neotropical Pselaphidae. 



Table X 

 SUBREGIONS OF NEOTROPICAL PSELAPHIDAE 



It will be noted that the South American area is not divided into a Chilean 

 and a Brazilian subregion of Wallace (1876). We have insufficient information 

 on pselaphids of Peru and Ecuador for such a division. The three subregions rec- 

 ognized have a sufficiently distinct pselaphid fauna to warrant their existence. 

 These three areas have an average taxonomic density of 1 : 4649, which by 

 coincidence is nearly that of Paraguay. 



