272 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



The chaetotaxy (figs. 4-9) schematically is as follows (the pleural 

 setae included in the tergal ones) : 



• "3a" is extremely short, not much longer than its pit. 



The most remarkable features are the following: 1. s VIII %. 

 Bonet (1949-50) divided the species of Eosentomon into groups ac- 

 cording to the number of setae in s VIII. The mexicanum group has 

 two anterior setae and no central posterior seta. The pallidum group 

 has no anterior setae; E. transitorium belongs to this group. E. 

 wheeleri, which has two anterior setae and a central posterior seta, 

 belongs to a third group. We may call this the wheeleri group. Tuxen 

 (1956b) shows that E. boneti belongs to the last group. 



2. The presence of "3" in the anterior row of t III-IV, making 

 a row of 12 setae. In boneti and mexicanum there are only 10 ante- 

 rior setae. In transitorium 12 anterior setae are present in t III-IV 

 as well as in V and VI, but these latter ones are missing in wheeleri. 



The accessory setae are longer than the principal ones, as is also 

 the case in mexicanum and especially boneti, but in transitorium they 

 are equal. Figure 10 shows this as well as the shape of the lamina, 

 anterior to the anterior apodeme. Figure 11 shows the sternal part 

 of the same segment. 



Tarsus III is provided with a distinct spine (fig. 12). 



The mouth parts are shown in figures 13-14. Until now the mouth 

 parts have not been used in the systematics of Eosentomon, but from 

 the description of the next species it is apparent that they may differ 

 widely within the genus. Those of wheeleri do not differ very much 

 from those of transitorium (Berlese 1909). 



Eosentomon vermiforme Ewing 



Figures 15-22 



Eosentomon vermiforme Ewing, 1921b, p. 194; 1910, p. 522. 



We have examined and drawn figures from the holotype and a 

 paratype slide of this species. The holotype was collected from decay- 

 ing leaves in Takoma Park, Maryland, by H. E. Ewing, February 14, 

 1921, and the paratypes in dead leaves from Plummers Island, 

 Maryland, by R. C. Shannon, March 18, 1924. The paratype slide 

 contains 1 male and 2 females; only the male has foretarsi. The 

 holotype specimen is a female. 



