22 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



regions of most of the body segments. Long outstanding simple 

 sensory setae are present on the occiput, coxae, and body segments, 

 occurring in a row across the middle of each of the first three abdominal 

 segments. Maximum length, 1.6 mm. 



In moderately pigmented specimens the pigment forms a reticula- 

 tion, marking off the hypodermis cells. In large heavily pigmented 

 individuals there are suggestions of three interrupted stripes above: 

 One median and two subdorsal. Furthermore, the body segments 

 are often margined posteriorly with blackish. Specimens show occa- 

 sionally a trace, dorsally, of the suture between the fourth and fifth 

 abdominal segments. The apical tooth of the mucro varies in length 

 and may be reduced or even absent (pi. 4, fig. 45). 



Remarks. — The preceding description was made from cotypes, 

 supplemented by specimens received from A. D. MacGillivray, 

 C. F. Baker, F. L. Harvey, and A. P. Morse. All tliis material was 

 collected at Fort ColKns, Colo., by C. F. Baker. 



Thirteen cotypes of bidenticula Guthrie, loaned to me through the 

 courtesy of Prof. H. F. Nachtrieb, proved to be tliis species. 



Folsomia elongata occurs on the ground under wood, dead leaves, 

 and stones; under loose bark; on pools of fresh water; and under 

 flowerpots in greenhouses. In central Illinois I have taken full-grown 

 specimens in abundance late in vdnter (February 4), and found the 

 species to be active, though sluggish, under logs during cold weather 

 when the ground was frozen. 



Distribution. — Recorded as follows: 



Maine: Orono, April 15, in moss from swamp, F. L. Harvey. 



Illinois: Homer, February 4, 5, 28, 29, March 14, 25, 31, April 2, 5, 6, 7, 8, 11, 13, 



16, 18, October 10, 23. Urbana, April 10, 11. 

 Iowa: Sioux City, January 29, C. N. Ainslie. 

 Kansas: Manhattan, February 3, D. B. Whelan. 



Minnesota: Minneapohs, December 16, J. E. Guthrie (University of Minnesota). 

 Colorado: Fort Collins, January 10, C. F. Baker (Museum of Comparative 



Zoology). Pikes Peak, July, August, Douglas-fir-forest soil (8,300 feet), 



G. W. Goldsmith. 



FOLSOMIA GUTHRIEI (Linnaniemi) 



Plate 5, Figures 47-49 



Isoloma minima Guthrie, 1903, p. 63. 

 Proisotoma guthriei Linnaniemi, 1912, p. 132. 



Description. — "Light grayish-blue in color, body subcylindrical, 

 elongate, almost naked except on the fifth and sixth abdominal seg- 

 ments, which bear some long scattered hairs. Fourth, fifth and sixth 

 abdominal segments apparently so fused as to form almost a con- 

 tinuous segment. Antennae gray, little longer than the head; Ant. 

 IV longest, very much swollen, III much rounded, shorter than II 

 and slightly longer than I. Ocelli 16. Post-antennal organ [fig. 47] 

 long, narrowly elHptical, slightly emarginate along anterior edge. 



