COLLEMBOLA OF THE FAMILY ISOTOMIDAE 21 



setae ; an additional seta occurring just in front of the corpus. Clothing 

 (pi. 4, fig. 39) short, slightly curving, longer posteriorly, simple; 

 sensory setae erect, relatively short, simple. Integument smooth. 

 Maximum length, 1.3 mm. 



Remarks.— Five individuals out of 18 had two eye spots on each 

 side, a large anterior and a small posterior spot. Other specimens 

 showed transitional stages between one eye spot and two. 



Cotypes.—V.S.^M. no. 42994. 



Distribution.— Recorded as follows: 



New York: New York Cit}', July, F. Silvestri, for whom the species is named. 



FOLSOMIA ELONGATA (MacGillivray) 



Plate 4, Figures 40-46 



Isotoma elongata MacGillivray, 1896, p. 49. 

 Isoioma hidenticula Guthrie, 1903, p. 66. 



Description. — Body slender, subcylindrical. General color mottled 

 grayish or greenish gray above, less often bluish or brownish; white 

 beneath; legs and furcula white; antennae white, or mottled with 

 pigment. Most of the body segments are pale anteriorly, giving 

 the eJEfect of whitish bands. Eyes (pi. 4, fig. 40) eight on each side, 

 unequal; ocular areas elongate. Postantennal organ (pi. 4, fig. 40) 

 narrowly elliptical or subelliptical; as wide as, and three or four times 

 as long as, the diameter of the adjacent eye. Antennae varying from 

 a little shorter to a little longer than the head, with segments in rela- 

 tive lengths about as 4:7:6:13 or 5:9:8:15. Sense organ of third 

 antennal segment (pi. 4, fig. 41) with two rods and three setae. 

 Fourth antennal segment with slender sensory setae. Last three 

 abdominal segments ankylosed, forming a smoothly rounded mass. 

 Anus ventrocaudal. Tibiotarsus without a distal subsegment. 

 Hind claws larger than the others. Unguis (pi. 4, fig. 42) stout, curv- 

 ing, without teeth. Unguiculus extending one-third (first pair) to one- 

 half or two-thirds (third pair) as far as the unguis, sublanceolate, 

 acuminate or setaceously produced, untoothed. Tenent hairs absent, 

 represented by a single simple hair, Furcula appended to the fourth 

 abdominal segment, short, extending only to the middle of the third 

 abdominal segment, in lateral aspect rapidly narrowing from a broad 

 base. Manubrium one-third to one-half longer than dentes, stout, 

 with several stiff dorsal setae and two long subapical ventral setae; 

 manubrial hooks well developed. Dens (pi. 4, fig. 43) stout, with five 

 or six dorsal crenulations beyond the middle. Mucrones (pi. 4, figs. 

 44, 45) bidentate; apical tooth almost straight or sUghtly hooked; 

 anteapical tooth frequently larger than the first tooth, suberect or 

 feebly curving. Tenaculum with quadridentate rami and a single 

 stout curving ventral seta. General clothing (pi. 4, fig. 46) of short 

 equal shghtly curving setae, absent on the anterior and posterior 



