COLLEMBOLA OF THE FAMILY ISOTOMIDAE 13 



of the antenna. Antennae a little shorter than the head; second 

 and third segments subequal in length; fourth almost twice as long 

 as the third. Sense organ of third antennal segment (pi. 2, fig. 13) 

 with a pair of linear, slightly curving rods subtended by a chitinous 

 ridge. Tliird antennal segment with a few olfactory setae; fourth 

 with many (Agren). Latter with two terminal sensory papillae: an 

 upper, stout globose or cordate; and a lower, elongate, curving, apically 

 rounded; subapical papilla also present. Abdomen rounded pos- 

 teriorly. First four abdominal segments subequal in length. Un- 

 guis (pi. 2, fig. 14) stout, untoothed. Ungidculus rudimentary, 

 spinelike. Tenent hairs 3 or 4, feebly knobbed (4 or 5, Stach). 

 Clothing (pi. 2, fig. 15) of sparse short rather stiff setae, with long 

 stiff sensory setae on the posterior part of the abdomen. Integument 

 reticulate, not tuberculate. Maximum length, 1.5 mm. 



Remarks. — From Dr. Schaffer I received European examples of 

 this species, with which the North American specimens that I have 

 seen (including those of Guthrie) agree. 



The largest tenent hairs are commonly three in number in specimens 

 from the United States. 



As Stach (1921) notes, the long sensory setae of the body are 

 knobbed, and there is one of these on each side of the mesothorax 

 and the metathorax. 



The unguiculus when rudimentary is variable in length, and in the 

 variety cuspidata Stach (1921) it is well developed. 



Variety ^JaZ^w/a Absolon (1901), which is whitish but intergrades 

 with the typical form, was taken in Bohemia, usually in caves though 

 sometimes under stones and in moss. 



Though its typical habitat is under loose bark, A. laricis occurs 

 also in such diverse situations as on the ground under wood, stones, 

 or dung; on fungi; on the surface of fresh water; and on snow. Ab- 

 solon found the species in small dry caves in Bohemia. 



Distribution. — This species, known from all parts of Europe and 

 from Siberia, is without doubt more widely distributed in North 

 America than the following few records indicate: 



New York: New York City, July, F. Silvestri. Lakeville, October 23, E. A. 



Maynard. 

 Minnesota: Lake Pepin, August 23, J. E. Guthrie (University of Minnesota). 

 Colorado: Eastern slope of Pikes Peak (8,300 feet), June, July, August, G. W. 



Goldsmith. 



Genus FOLSOMIDES Stach 



Folsomides Stach, 1922a, p. 17. 



Genotype. — Folsomides parvulus Stach. 



Body cylindrical, greatly elongate, segments not strongly imbricate. 

 Prothorax imusually long. The abdominal segments are simple 

 rings, subequal in length (except the anal segment) and without 



95462 — 37 2 



