32 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



This variety caldaria differs in several respects from the variety 

 dentata Folsom (1927). 



Distribution. — Recorded as follows: 

 New York: Ithaca, November 5, working in decayed tissue due to work of a 

 tortricid larva near bases of stems of Ivipatiens 'pallida, Mrs. L. A. Hausman. 



FOLSOMIA NIVALIS (Packard) 



Plate 8, Figures 81-88 



Isotoma nivalis Packard, 1873, p. 31. — MacGillivrat, 1891, p. 273; 1896, p. 

 53. — VON Dalla Torre, 1895, p. 10. 



Description. — White throughout; a slender species. Eyes absent. 

 Postantennal organs (pi. 8, figs. 81, 82) long and narrow, about nine 

 times as long as broad, four-fifths as long as the basal width of the 

 first anteunal segment, straight or slightly curving, with usually a 

 minute notch at the middle of the anterior margin. Antenna! base 

 well developed. Antennae as long as, or slightly longer than, the 

 head (about as 31:29) with segments in relative lengths about as 

 5:7:6:10 or 8:12:11:22. Sense organ of third antennal segment 

 (pi. 8, fig. 83) \vdth a pair of subclavate rods subtended by a thick 

 chitinous ridge. Fourth antennal segment with slender olfactory 

 setae. Unguis (pi. 8, fig. 84) long, slender, curving, unidentate near 

 the middle of the inner margin; lateral teeth absent. Unguiculus 

 one-third (first pair of feet) to one-half (second and third pair) as 

 long as unguis, broadly lanceolate, acuminate, untoothed. Tenent 

 hairs absent. Last three abdominal segments ankylosed. Anus 

 ventrocaudal. Furcula appended to the fourth abdominal segment, 

 and extending to the middle of the second. Dentes one and one- 

 half times as long as manubrium, slender, crenulate dorsally, the 

 crenulations absent on the distal fifth. Mucrones a little longer 

 than hind unguiculi, bidentate (pi. 8, figs. 85-88); apical tooth sub- 

 horizontal or slightly hooked; second tooth erect or suberect, conical, 

 stouter and usually longer than the apical tooth. Tenaculum 

 quadridentate, with one stout ventral seta. General clothing of 

 short curving simple setae. Long stiff simple sensory setae occur in 

 a transverse row across the middle of the first three abdominal seg- 

 ments, and numerously on the ankylosed segments. Usual length, 

 1 mm; maximum, 1.7 mm. 



The tooth of the unguis, usually strong, is sometimes reduced or 

 absent. The apical tooth of the mucro is reduced occasionally; the 

 anteapical tooth rarely (pi. 8, figs. 87, 88). 



Remarks. — The foregoing description is based on six of Packard's 

 cotypes from Brunswick, Maine, supplemented by an abundance 

 of specimens collected at Orono, Maine, by Prof. F. L. Harve3^ 



The specimens from Salem, Mass., referred to by Packard (1873) 

 were missing from the collection in the Museum of Comparative 

 Zoology. 



