COLLEMBOLA OF THE FAMILY ISOTOMIDAE 



61 



tending half as far as the unguis, untoothed. Tenent hairs absent. 

 Furcula extending only to the middle of the second abdominal seg- 

 ment. Manubrium two-thirds as long as dentes, with many short 

 dorsal setae and one pair of stout subapical ventral setae. Dentes 

 slender, gradually tapering, crenulate dorsally, with many ventral 

 setae. Mucro (pi. 23, fig. 255) a little longer than hind unguiculus 

 (as 13:11), subequally bidentate; apical tooth upcurving, second 

 suberect. Rami of tenaculum quadridentate; corpus Avith a single 

 stout seta. General clothing of abundant rather stiff simple setae 

 of moderate length; sensory setae outstanding, stiff, relatively stout, 

 simple. Length, 0.5 mm. 



Remarks. — This species is close to angularis Axelson (1905), from 

 which it differs as shown in table 3. 



Table 3. — Comparison of Proisotoma angularis and P. decemoculata 



Cotypes.—U.S.^M. no. 42990. 

 Distribution. — Recorded as follows: 

 Illinois: Homer, April 6 and 9, under a stone on grass. 



PROISOTOMA (PROISOTOMA) SIMPLEX, new species 



Plate 23, Figures 256-258 



Description. — Wliite, mottled with gray or black pigment. Body 

 segments bordered posteriorly wdth black. Antennae mottled with 

 black; legs and furcula white. A black A-shaped mark extends for- 

 ward from the eyes. Eyes eight on each side, subequal. Post- 

 antennal organ (pi. 23, fig. 256) subelliptical, a little more than twice 

 as long as the diameter of an adjacent eye. Antennae one-fifth longer 

 than the head, with segments in relative lengths about as 3:6:5:10. 

 Sense organ of third antennal segment with a pair of minute linear 

 naked rods. Fourth antennal segment without special olfactory 

 setae. Third abdominal segment shorter than the fourth (as 5:6). 

 Genital and anal segments not ankylosed. Tibiotarsus with a trace 

 of a distal subsegment. Unguis (pi. 23, fig. 257) feebly curving, un- 

 toothed. Unguiculus lanceolate, untoothed, extending three-fifths 

 as far as the unguis on the hind feet, and half as far on the other feet. 

 One tenent hair. Furcula not attaining the ventral tube, but extending 

 to the middle of the second abdominal segment. Manubrium stout, 

 with a few dorsal setae and three pairs of ventral subapical setae. 

 Dentes scarcely longer than the manubrium, stout, tapering, with 



95462—37 5 



