COLLEMBOLA OF THE FAMILY ISOTOMIDAE 59 



appended to the fifth abdominal segment, not attainmg the ventral 

 tube but extending as far as the second abdominal segment, stout. 

 Manubrium about seven-eighths as long as dentes, setigerous on all 

 sides. Dentes stout, not tapering, broad apically, each with a lateral 

 protuberance one-fourth from the base, and \vith about eight large 

 dorsal semicircular folds. Dentes with a few setae dorsally, and many 

 stiff setae laterally and ventrally. At the end of the dens is a con- 

 spicuous lateral expansion in the form of a transparent bladder (pi. 

 22, figs, 242, 243) extending half the length of the mucro. Mucro 

 (pi. 22, figs. 242, 243) stout, quadridentate. Apical tooth small, 

 slightly curving or almost straight; second and third teeth in line with 

 the first, subequal, directed slightly forward; fourth tooth lateral, 

 oblique. Ventral contour of mucro in lateral aspect almost straight 

 proximally. Rami of tenaculum quadridentate; corpus with three 

 ventral setae. General clothing (pi. 22, fig. 244) of short strong 

 curving simple setae, becoming longer on the genital and anal seg- 

 ments. Erect sensory setae apparently absent. Integument 

 minutely tuberculate, becoming smooth and reticulate on the posterior 

 regions of the body segments and on the intersegmental membranes. 

 The coarse dorsal tubercles of the anogenital segment form several 

 crenulate ridges. Length, 1.2 mm. 



Cotypes.—V.S.'NM. no. 42989. 



Distrihution. — Recorded as follows: 

 Maine: Orono, March 10, in moss in pine woods, F. L. Harvey. 



PROISOTOMA (PKOISOTOMA) AQUAE (Bacon) 



Plate 22, Figures 245, 246; Plate 23, Figures 247-252 

 Isotoma aquae Bacon, 1914, p. 147. 



Description. — General color gray, with a bluish or greenish tinge; 

 mottled blue and yellow. The pigment forms a reticulation around 

 the borders of the hypodermis cells. Intersegmental regions unpig- 

 mented, appearing as white bands. Antennae and bases of legs 

 mottled with pigmient; manubrium pigmented. Eyes (pi. 22, fig. 245) 

 eight on each side, unequal. Ocular patches black, usually two on 

 each side (pi. 22, fig. 246); an anterior, with five eyes, and a posterior, 

 with three eyes. Postantennal organ (pi. 22, figs. 245, 246; pi. 23, 

 fig. 247) subelliptical, constricted near the muddle, thick-walled, three 

 to three and one-half times as long as the diameter of an adjacent eye. 

 Antennae slightly longer than the head (as 8:7), ■\\dth segments vary- 

 ing in relative lengths but frequently as 16:25:27:50. Sense organ 

 of third antennal segment (pi. 23, figs. 248, 249) with a pair of sub- 

 clavate, slightly cm-ving, oblique sense rods immersed in a pit and 

 subtended by a thick cuticular fold. Olfactory setae of fom-th anten- 

 nal segment not clearly differentiated from ordinary setae. Third 

 abdominal segment shorter than the fourth (as 6:7 or 7:8). Genital 



