266 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



For the systematics of the Protura it seems of paramount importance 

 to be able to define with certainty which species the first describers 

 had before them. In his redescriptions of the species described by 

 Berlese and Silvestri, Tuxen (1956) stressed characters not known 

 by these authors: The setae and sensillae of the foretarsus, the female 

 genital squama, and the chaetotaxy. In 1958 Tuxen did the same for 

 a species described by Stach. In the present paper a similar study has 

 been made of the species which were described by Ewing and are now 

 kept in the U.S. National Museum, Washington. 



Ewing described his species in several papers. In 1921 he described 

 Acerentulus barberi, the first American proturan to be identified since 

 Silvestri's specimen, collected in the vicinity of New York in 1909 

 and called Eosentomon wheeleri. The type specimen of wheeleri was 

 supposed lost, until its rediscovery was reported by Tuxen (1960). 



In 1921 Ewing also described 10 more species from the United 

 States. They were placed in three old and three new genera. The 

 specimens were all found near Washington, D.C. The next year he 

 briefly mentioned the then known distribution of Protura in the United 

 States. In 1924 he described a new species from Florida, and in 1927 

 a new species from the western states. In 1936 he compiled a "syn- 

 onymy and synopsis" of the genera then known. A larger paper in 

 1940 summed up all the knowledge of the North American Protura and 

 contained the descriptions of six new species. Thus 19 species were 

 described by Ewing, besides the redescription of E. wheeleri Silvestri. 

 Of these species, he identified A. tenuiceps as a synonym of A. barberi 

 and, erroneously, E. minimum as a synonym of E. pallidum in 1940. 

 The types of the remaining species will be discussed in the present 

 paper. 



The 1940 paper by Ewing is based on much more material than the 

 types, in all about 200 slides. Part of this material is incorrectly deter- 

 mined and part of it probably comprises new, hitherto undescribed 

 species, but it does not seem advisable to describe more species as long 

 as the species of Ionescu and Womersley have not been reexamined. 

 In 1960 Tuxen finished this task. 



A small, ridiculous difficulty in describing arose. In 1949 both of us 

 invented systems of numbering the dorsal abdominal setae, but 

 unfortunately in opposite directions, Tuxen made the median setae 

 No. 1 , while Bonet made the lateral ones No. 1 . Bonet used his system 

 in 1949 and 1950. Tuxen used his system in 1949 and in the papers 

 since 1955. Among the latter were the redescriptions of Berlese's and 

 Silvestri's species. Since it is easier to define the position of the median 

 setae than that of the lateral ones (the pleura are not always distin- 

 guishable from the terga), the "Tuxen-system" of numbering will be 



