106 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



This new species occurred in large numbers in moss on rock bluffs, 

 and in some of the individuals the mid-intestine was full of moss 

 spores. 



Cotypes.—U.S.NM. no. 42969. 



Distribution. — Recorded as follows: 



Illinois: Alto Pass, March 4, T. H. Frison and H. H. Ross (Illinois State Natural 

 History Survey). Makanda, March 5, T. H. Frison and H. H. Ross (Illinois 

 State Natural History Survey). 



ISOTOMA aSOTOMA) GEUDA. new species 



Plate 35, Figures 412-417 



Description. — General color olive-green to purple, densely flecked 

 with minute unpigmented spots; with wide whitish intersegmental 

 bands. Front with a transverse purple mark including the antennal 

 bases, and extending back between the eyes as a median dorsal mark. 

 Antennae purple; first segment paler; second and third often pale 

 proximally. Legs greenish or purplish basally, whitish beyond coxae; 

 tibiotarsi white or pale purplish. Furcula white. Eyes eight on each 

 side, the two inner proximal smaller than the others. Postantennal 

 organ (pi. 35, figs. 412, 413) elliptical, one-third to three-fifths longer 

 than the diameter of an adjacent eye. Antennae one-half to two- 

 thirds longer than the head, with segments in relative lengths about 

 as 9:15:16:18; second and tliird segments subclavate; fourth ellip- 

 tical. Sense organ of third antennal segment (pi. 35, fig. 414) 

 with a pair of rods and two guard setae; the integument in the 

 region of the organ being roughly and irregularly tuberculate. Fourth 

 antennal segment without special olfactory setae. Third and fourth 

 abdominal segments equal, or third slightly longer than the fourth 

 (as 23:20). Genital and anal segments ankylosed, with a trace of a 

 dorsal suture. Unguis (pi. 35, fig. 415) slender, with a pair of large 

 lateral teeth and a small tooth at the middle of the inner margin. 

 Unguiculus broadly lanceolate, acuminate, untoothed, extending 

 five-sevenths as far as the unguis on the hind feet, and about one- 

 half as far on the other feet. Tenent hairs absent. Furcula extending 

 to the ventral tube. Manubrium with dense short setae dorsally and 

 ventrally. Dens about twice as long as manubrium, slender, dorsally 

 rather coarsely crenulate, the folds merging into coarse tubercles near 

 the mucro ; with numerous erect dorsal setae and many short appressed 

 ventral setae. Mucro (pi. 35, figs. 416, 417) four-fifths as long as 

 hind unguiculus, quadridentate; apical tooth hooked; anteapical 

 tooth the largest, with a pair of lamellae extending from its apex to 

 the base of the mucro; third tooth much smaller than the second, 

 erect or slightly oblique, with a small lamella; fourth tooth lateral, 

 almost opposite the tliird, oblique and acute or erect and blunt. 

 Rami of tenaculum quadridentate; corpus with 25 or more setae of 

 different sizes. General clothing of dense stiff simple setae of various 



