COLLEMBOLA OF THE FAMILY ISOTOMIDAE 73 



Legs of the body color, dark basally; furciila unpigmented or with 

 some pigment on the manubrium. Eyes (pi. 26, fig. 284) eight on 

 each side of the head, subequal; or the two inner proximal eyes of each 

 group a little smaller than the others. Postantennal organ (pi. 25, 

 fig. 284) near the eyes, elliptical, slightly longer than, to twice as long 

 as, the diameter of an adjacent eye. Antennae one and one-half to 

 two times as long as the head, with segments in relative lengths about 

 as 3:4:5:6; first segment pale, or bluish apically; second and third 

 pale, bluish apically; fourth bluish tliroughout. Sense organ of third 

 antennal segment with a pair of linear feebly curving rods, a thick 

 basal ridge, and two guard setae. Very short curving sensory setae 

 occur on all the antennal segments as follows: Segment 1, 2-5; 2, 

 3-7; 3, 3-7; 4, 10-15. On the first thi-ee segments these are on the 

 under side near the distal outer end ; on the fourth segment they occur 

 on the distal half along the outer side (Agren, 1903). Mesonotum 

 almost covering the pronotum. Third abdominal segment a little 

 longer than the fourth (about as 5:4). Abdominal segments without 

 ankylosis. Unguis (figs. 285, 286) stout, curving, with a pair of small 

 lateral teeth, and with inner margin untoothed. Unguiculus broadly 

 lanceolate, with inner lamella roundly dilated basally, untoothed as a 

 rule, extending about half as far as the unguis on the hind feet, shorter 

 on the other feet. Tenent hairs absent, represented by a single long 

 simple hair. Furcula appended to the fifth abdominal segment, and 

 extending to the anterior border of the ventral tube. Manubrium 

 with many stiff ventral setae. Dentes twice as long as manubrium, 

 slender, gradually tapering, crenulate dorsally. Mucro (pi. 26, figs. 

 287, 288) two-thirds as long as hind unguis, quadridentate. Apical 

 tooth of mucro small, at the base of the second tooth; second and 

 third teeth dorsal, large, subequal, subconical, in line with the first 

 tooth; fourth tooth lateral, oblique, acute; a membrane extends on 

 each side from the apex of the third tooth to the base of the mucro; 

 basolateral mucronal seta present. Rami of tenaculum quadriden- 

 tate (pi. 26, fig. 289); corpus with many (15 or more) ventral setae. 

 General clothing of abundant short simple setae. The second to 

 fourth abdominal segments, inclusive, bear on each side three long 

 attenuate feathered bothriotricha (pi. 26, fig. 290). Length, 3 mm. 



Remarks. — The ungues vary in stoutness (pi. 26, figs. 285, 286). 



The statement regarding bothriotricha is from Borner. They vary 

 somewhat in number and position, and' may occur on the last five 

 abdominal segments. 



North American examples of palustris agree accurately with the 

 European specimens that I have received from Dr. C. Schaffer and 

 Dr. Jan Stach. 



Packard's six cotypes of his Isotoma tricolor, from Waco, Tex., in 

 the Museum of Comparative Zoology, Cambridge, Mass., for which 



