COLLEMBOLA OF THE FAMILY ISOTOMIDAE 67 



and low arched; oral region elongate. Eye spots elongate. Eyes 

 (pi. 14, fig. 147) eight on each side, the two inner proximal eyes 

 much smaller than the others. Postantennal organ (pi. 14, fig. 147) 

 elongate, narrowly elliptical, one and one-half to four times as long 

 as the diameter of the adjacent eye. Antennae usually as long as, or 

 slightly longer than, the head; in some individuals 1.7 times as long, 

 however. Antennal segments in relative lengths about as 3:4:5:4 or 

 8:10:9:12; the last segment being, therefore, relatively short. Sense 

 organ of third antennal segment with two feebly curving rods sub- 

 tended by a cliitinous ridge, which is sometimes absent, however. 

 Fourth antennal segment with two or three dorsolateral curving 

 blunt olfactory setae, with terminal lobe and subapical papilla. 

 Femur and tibiotarsus each with a distal subsegment (pi. 14, figs. 

 148, 149) on all the legs. Hind femur with a distal outer thornlike 

 process (pi. 14, fig. 149). Unguis (pi. 14, fig. 148) narrow, curving, 

 without lateral teeth and without an inner tooth (often with a small 

 inner tooth according to Linnaniemi, 1912). Unguiculiis extending 

 three-fourths as far as unguis, broadly sublanceolate, apically seta- 

 ceous, untoothed, with outer lamella absent, and with a pair of inner 

 lamellae. Tenent hairs absent. Third and fourth abominal 

 segments subequal, or third a little shorter than fourth (as 7:8). 

 Fifth and sixth abdominal segments almost or completely ankylosed; 

 there being, however, in some specimens, particularly in small indivi- 

 duals, a faint short dorsal suture between the two segments. The 

 last two abdominal segments project conspicuously beyond the base 

 of the furcula, which arises (apparently) from both the fourth and 

 fifth abdominal segments. Furcula stout, of almost uniform thick- 

 ness, extending not quite to the ventral tube. Manubrium long, 

 slender, with a long coxal, or basal, segment; with many longer or 

 shorter stifT dorsal setae and naked ventrally. Manubrium equal 

 to dens plus mucro in length. Dentes stout, not tapering distally, 

 rounded apically, not crenulate or tuberculate dorsally, with many 

 short setae dorsally and ventrally. Mucrones (pi. 15, figs. 150, 151) 

 about as long as hind unguiculi, tridentate, with a large apical tooth 

 and a pair of large dorsolateral basal teeth subtriangular in lateral 

 aspect. Mucrones strongly asymmetrical in dorsal aspect (pi. 15, 

 figs. 152, 153). Lateral mucronal seta present. Rami of tenaculum 

 (pi. 15, fig. 154) quadridentate; corpus with a large subcorneal anterior 

 accessory lobe, and without setae. General clothing of dense short 

 simple setae (pi. 15, fig. 155), becoming longer on the posterior part 

 of the abdomen. Long outstanding simple setae occur also on all 

 the body segments. Abdominal bothriotricha (exceptionally long, 

 slender, naked hairs) at least two pairs (see beyond). Integument 

 smooth. Length, usually 1-1.5 mm; maximum, 2.1 mm. 



Remarks. — Denis (1924c) found two pairs of bothriotricha on the 

 anal segment. I note two pairs situated as follows: (1) A pair on the 



