COLLEMBOLA OF THE FAMILY ISOTOMIDAE 107 



lengths; outstanding sensory setae long, simple. Maximum length, 

 2.4 mm. 



Cotypes. — U.S.N. M. no. 42974. All the cotypes were taken in 

 March; some near a stream, others on ice. 



Distribution. — Recorded as follows: 



Illinois: Carbondale, March 4, T. H. Frison and H. H. Ross (Illinois State 

 Natural History Survey). Oakwood, March 3, 11, 17, T. H. Frison (Ilhnois 

 State Natural History Survey). 



ISOTOMA aSOTOMA) SUBAEQUALIS, new species 



Plate 36, Figures 418-421 



Description. — General color olive-green to purple,' darker dorsally, 

 thickly mottled with pale spots of various forms and sizes, with 

 narrow whitish intersegmental bands. Head with a dorsomedian 

 wide irregular mark and a frontal A -shaped mark connecting the 

 eye spots. Antennae dull purplish throughout, or with the first 

 segment and the base of the second greenish. Legs and furcula 

 pale green or pale purplish. Eyes eight on each side, the two inner 

 proximal eyes smaller than the others. Postantennal organ (pi. 36, 

 fig. 418) eUiptical, one and one-half times as long as the diameter of 

 an adjacent eye. Antennae one and one-half times as long as the 

 head, with segments in relative lengths about as 11:22:22:23. 

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

 exposed rods. Third abdominal segment from one-ninth to one-sixth 

 longer than the fourth. Genital and anal segments not ankylosed. 

 Anal valves conspicuous, triangular. Unguis (pi. 36, fig. 419) 

 rather slender, not strongly curving, wealdy unidentate near the 

 middle of the inner margin, and with strongly developed lateral 

 teeth, which are dentate or fringed distally. Unguiculus extending 

 three-fourths as far as the unguis on the hind feet (shorter on the 

 other feet), broadly lanceolate, untoothed, with an inner basal lobe. 

 Tenent hairs absent. Furcula attaining the ventral tube. Manu- 

 brium about one-half as long as dentes, with many short setae on all 

 sides. Dentes crenulate dorsally, setigerous on all sides. Mucrones 

 (pi. 36, figs. 420, 421) almost as long as hind unguiculi, with a baso- 

 lateral seta, quadridentate; apical tooth strong, hooked; anteapical 

 usually larger, erect; third tooth lateral, oblique, acute; fourth 

 conical, erect, in line with the first two teeth; an outer and an inner 

 lamella extend from the second tooth to the base of the mucro, and 

 a third lamella extends from the lateral tooth to the base. Rami of 

 tenaculum quadridentate; corpus with many anterior setae. General 

 clothing of abundant stiff setae of irregular lengths. Length, 2.3 mm. 



The most distinctive characters of subaequalis are the subequality 

 of the last tlu-ee antennal segments and the large size and fringed 

 condition of the lateral teeth of the ungues. 



