COLLEMBOLA OF THE FAMILY ISOTOMIDAE 99 



longer than the fourth (as 12:11); occasionally equal to fourth. 

 Furcula appended to the fifth abdommal segment and extending to 

 the ventral tube. Manubrium with many dorsal and ventral setae. 

 Dentes more than twice as long as manubrium (as 44:19), slender, 

 gradually tapermg, dorsally crenulate, the crenulations disappearing 

 at a distance from the mucro equal to two and one-half times the 

 length of the latter. Mucro three-fourths as long as hind unguiculus, 

 quadridentate (pi. 32, figs. 366-369). Apical tooth the longest, hooked. 

 Anteapical tooth a Httle shorter, conical, erect or slightly incUned. 

 Third and fourth teeth subequal, almost opposite each other, oblique 

 or suberect, one of them being lateral in position. Rami of tenaculum 

 (pi. 32, fig. 370) quadridentate; corpus with several (5 to 10) setae. 

 Clothing (pi. 32, fig. 371) of dense stiff simple setae, rather short, 

 becoming longer posteriorly; with a transverse row of longer suberect 

 simple setae across the middle of most of the body segments. Length, 

 1.5 mm (2 mm in large European individuals). 



The antennal segments vary greatly in relative lengths, which 

 may be expressed approximately, however, as 8:11:10:17 or 7:16:13:21; 

 occasionally there occurs such a formula as 4:7:7:12. 



Remarks. — In European specimens that I have seen the unguis had 

 small lateral teeth, the inner tooth of the unguis and the tooth of the 

 unguiculus being present or absent. In specimens from Canada and 

 Greenland all these teeth were strong. 



My European material of tliis species consists of Swedish specimens 

 determined by Dr. Schott and sent to me by Dr. Schaffer; others 

 from Finland, received from Dr. Linnaniemi; and Poland examples 

 from Dr. Stach. 



I sent Canadian specimens to Dr. Stach, who agreed with me that 

 they were olivacea. 



I. olivacea is found on the ground under stones, wood, or dead 

 leaves, under bark, and often in moss. According to Linnaniemi, 

 olivacea prefers damp, even wet, situations, and may be found in 

 great abundance in sphagnum moss and on pools of water. Although 

 a typical summer species, it may occur in winter in thawing weather, 

 and has been taken in winter on snow and in puddles of water on the 

 ice. 



Distribution. — This species, which has been reported from Norway, 

 Sweden, Denmark, Finland, Russia, Poland, Germany, Austria, 

 Hungary, Bohemia, and England, is in northern Europe one of the 

 most abundant coUembolans. 



New York: Albany, May 7, D. B. Young (New York State Museum). Rochester, 



March 9, E. A. Maynard. 

 Illinois: Homer, March 31, April 9. 



Canada: Arnprior, Ontario, November, April, May 1, C. Macnamara. 

 Greenland: Umanali, July 22, in moss, W. E. Ekblaw (American Museum of 



Natural History; University of Illinois). 



