24 
Psyche 
[March 
Connecticut; taken in humus in a mature white pine-hem- 
lock stand, 19 December 1950. 
Paratypes: same locality, October and December 1950; 
February, May, and August 1951. Eleven specimens. 
Also taken once in humus under cedars in the outer zone 
of an acid bog, Bethany, New Haven Co., Connecticut. 
The holotype will be deposited in the Museum of Com- 
parative Zoology, Harvard University. One paratype will 
be sent to the California Academy of Sciences, San Fran- 
cisco, Calif., and one to the United States National Museum, 
Washington, D. C. The remaining paratypes are in the 
author’s collection. 
Micrisotoma cannot be distinguished from other genera 
of Isotomidae by any single character. The form of the 
postantennal organ will distinguish it from other isotomids 
in the holarctic region, but Isotomina interrupta Schott, 
from Camercons, is said to have a similar organ (Stach 
1947; the original description is not available to me), and 
some species of Proisotoma approach it in this respect 
(Folsom 1937, figs. 245, 246, and 273). The subsegmented 
tibiotarsus allies it to Proisotoma Borner, and the fused 
abdominal segments and absence of eyes to Proisotomina 
Salmon; from both genera it is distinguished by the pres- 
ence of serrate setae. In vestiture and general appearance 
it resembles Isotomiella Bagnall, which, however, lacks a 
postantennal organ. 
Micrisotoma achromata appears to be relatively uncom- 
mon in the two situations in which it has been found so far. 
It is possible that it is a marginal species in these areas, 
and that its environmental optimum is somewhat different. 
The species has not been seen alive; specimens in alcohol 
are indistinguishable from Isotomiella minor Schaffer, 
which is common in the same samples. 
Bibliography 
Folsom, J. W. 
1937. Nearctic Collembola or Springtails, of the Family Isotomidae. 
U. S. Nat. Mus. Bull. 168. 
