COLLEMBOLA OF THE FAMILY ISOTOMIDAE 117 



terminal joint, as in /. albella, ending in a curved hook, with a supplementary- 

 one near it, much as in that species. The spring is slightly more hairy. The feet 

 and tarsal claws are much as in /. albella, but the tibiae have stouter spinules. 

 Sucker as long as the thoracic segments are thick. 



In two specimens I have observed the tenaculum. When retracted its side is 

 indicated by a flattened, conical swelling, with two stout hairs arising from each 

 side. When extended it has the same general structure as in the tenaculum of 

 Achorutes, but is much longer and slenderer; the basal portion or valve is about 

 twice as long as broad, square at the end; the second joint or valve is very narrow, 

 half as long as first joint is wide, with about four rounded teeth along the inner 

 edge. 



Length, .05 inch. 



Found very abundantly under bark in excrement of boring beetles. Salem, 

 Mass. (Packard). 



This species differs from /. albella, its nearest ally, in its stouter, shorter body 

 and antennae, and broader eye patches, and its bluish gray color. 



Remarks. — Plate 39, figure 450, is a copy of a pencil drawing made 

 by Packard during his study of this species. 



Among Packard's types in the Museum of Comparative Zoology, 

 I found two tubes labeled glauca ("under bark, Salem, May 22"), 

 neither of which contained any specimens. 



MacGillivray's specimens of glauca in that museum, as well as 

 those in the Cornell collection, proved to be viridis. 



Packard's glauca is evidently not viridis, at any rate. 



ISOTOMA TRIDENTATA MacGUIivray 



Plate 39, Figures 451-454 



Isoioma tridentata MacGillivray, 1896, p. 51. 



Description. — Yellowish; body segments narrowly edged behind 

 with purplish; antennae yellowish, with first and second segments 

 purplish apically, and third and fourth purplish except basally; 

 legs white; furcula white. Eye spots black, elongate. Eyes eight 

 on each side. Postantennal organs not studied. Antennae one and 

 one-half times as long as the head, with segments in relative lengths 

 about as 3:5:6:8. Third abdominal segment a little longer than the 

 fourth (as 6:5). Genital and anal segments not ankylosed. Unguis 

 (pi. 39, fig. 451) with a pair of lateral teeth and with inner margin 

 unidentate one-third from the apex; outer surface with a rounded 

 protuberance about one-third from the base. Unguiculus broadly 

 lanceolate, acuminate, unidentate. Tenent hau's absent. Furcula 

 appended to the fifth abdominal segment, extending as far as the 

 ventral tube. Manubrium cylindrical. Dentes more than twice 

 as long as the manubrium, slender, tapering, crenulate dorsally. 

 Both manubrium and dentes have numerous dorsal setae and dense 

 stiff ventral setae. Mucro (pi. 39, figs. 452-454) subequally tri- 

 dentate, the teeth subfalcate; third tooth lateral. Clothing of 

 dense setae of various lengths. Abdomen -with, dense stiff ventral 

 setae. Strong outstanding unilaterally serrate setae occur in clusters 



