20 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



Unguis with lateral teeth and an inner tooth. Tenent hairs 

 present. Manubrium with many ventral setae. White, 

 mottled with blue silvestrii (p. 20) 



6. Eyes four or two. Manubrium longer than dentes. Dentes 



with a few small dorsal crenulations in the middle region. 



Unguis untoothed 7 



Eyes six. Manubrium shorter than dentes, or the two occa- 

 sionally subequal. Unguis with lateral teeth but no inner 

 tooth. Gray to blackish sexoculata (p. 23) 



7. Eyes four. Gray to blackish quadrioculata (p. 24) 



Eyes two. White diplophthalraa (p. 27) 



FOLSOMIA SILVESTHII, new species 



Plate 4, Figures 35-39 



Description. — White, mottled with bhie; anterior borders of body 

 segments white; posterior borders of mesonotum to third urotergite, 

 inclusive, edged narrowly with dark blue. First and second antennal 

 segments mostly white but mottled with blue; third and fourth seg- 

 ments blue. Legs white, with more or less pigment except on tibio- 

 tarsi. Manubrium pigmented basally; dentes unpigmcnted. Eyes 

 (pi. 4, fig. 35) eight on each side, the two inner proximal eyes much 

 smaller than the others. Postantennal organ (pi. 4, figs. 35, 36) 

 elongate subelliptical, from three and one-half to six times as long as 

 wide, and three to five times as long as the diameter of an adjacent 

 eye, with a notch near the middle of the anterior margin. Antennae 

 equal to head in length or a little shorter (as 9:10); third segment 

 shghtly longer than the second; fourth about twice as long as the 

 third, stout, elliptical. Sense organ of third antennal segm.ent with 

 a pair of short pegs subtended by a chitinous thickening. Fourth 

 antennal segment without special olfactory setae. Last thi-ee ab- 

 dominal segments ankylosed, forming a single mass, rounded posteri- 

 orly; anus ventrocaudal. Tibiotarsi with a distal subsegment, 

 sometimes incomplete. Unguis (pL 4, fig. 37) stout, with a pair of 

 small lateral teeth and an inner tooth (sometimes absent) two-fifths 

 from the apex. Unguiculus broadly lanceolate, acuminate, with 

 inner lamella strongly rounded basally; extending two-thirds as far 

 as the unguis on the hind feet, and about half as far on the other feet. 

 Tenent hairs 1, 2, 2 or 2, 2, 2; one of the two hairs being stronger than 

 the other. Furcula (pi. 4, fig. 38) short, extending only to the second 

 abdominal segment. Manubrium longer than dentes (as 9:7); ven- 

 trally with many stiff setae and a subapical pair much longer and 

 stouter than the others. Dentes with a few dorsal crenulations in 

 the middle region that become smaller distally; ventrally with a 

 moderate number of stiff setae. Mucrones (pi. 4, fig. 38) one-fourth 

 longer than hind unguiculi, bidentate; apical tooth smaller than the 

 anteapical and slightly hooked; second tooth erect. Tenaculum 

 quadridentate ; corpus with either one or two strong curving anterior 



