Springiails (Collembola) of the St. Louis Area 23 
Records: February 5, 1938, under bark of willow tree, Vinita 
Terrace, St. Louis County, Missouri, (E. D, Bueker)y. 
FAMILY Sminthuridae Lubbock, 1870 
Antennae longer than the head, inserted near the vertex; 
the antennae four-segmented, with the fourth segment subdivided 
into segments, sometimes the third is also subdivided. Thorax 
is small, with abdomen much rounded and having an anal papilla. 
GENUS Ptenothrix Borner, 1906 
Third and fourth antennal segments are subdivided. Dentes 
dorsally with large serrate setae. 
Ptenothrix unicolor (Harvey), 1893 
Figures 29-31; length 1.5-2 mm.; brown to dark brown; an- 
tennae almost as long as the body, third and fourth segments 
Subsegmented, between the proximal segment of the third and 
the enlarged apical segment of the third are six subequal short 
Segments, fourth segment with four short subequal segments and 
a longer apical conical segment; each eyespot with eight eyes; 
unguis with two inner teeth and two lateral teeth; unguiculus 
With a well-developed inner tooth and an apical seta which ex- 
tends beyond the unguis; each dorsal margin of the unguis with 
approximately 19-24 serrate-like teeth. 
This form is commonly found under logs, bark, and in humus. 
Records: November 22, 1936, Grimbsy, St. Louis County, Mis- 
Souri, (Leslie Hubricht). 
