1 a Canadian Arctic Expedition, 1913-18 



middle of the inner margin. Unguiculus represented only by a fcoothlike rudi- 

 ment. Tenenl hair single, unknobbed. Rami of tenaculum quadridentate. 

 Furcula very long, exl 'nding as far as the first pair of legs, clearly appended to 

 the fourth abdominal segment. Manubrium short. Dentes long, strongly 

 bowed outward, apically convergent, with an obsolete transverse suture two- 

 fifths from the bas >, and with the tubercles of the distal third arranged in trans- 

 verse rings. Mucrones figs. 2, 3) three-fifths as long as hind ungues, with outer 

 and inner lamellae, and with a prominent dorsal rounded-triangular basal lobe. 

 Anal spines absent. Body clothing of few minute curving setae; dens with 12 

 to 17 long curving dorsal setae, most of which arc in two longitudinal scries. 

 Integument t uberculal Lengt h. 1 . 3 nun. 



Podura aquatica, one of the most abundant collembolans in Europe and 

 North America, occurs on the surface of standing water on the margins of ponds 

 and streams, having special structural adaptations for a s mi-aquatic life. It 

 swarms on vegetation or rubbish along the shore, and at times is blown against 

 the shore in masses of enormous numbers. This specie- often appears in fresh- 

 water aquaria, and is essentially a fresh-water species, though it has been found 

 occasionally in pools of brackish water on the seashore. 



The species has been recorded from Siberia. From Canada, I have speci- 

 mens taken at Amprior. Out.. May L9, 1017, by Mr. Charles Macnamara. 



Great numbers on ponds, Demarcation point. Alaska. May 16, 1914; 

 abundant, large and small, at Bernard harbour, Dolphin and Union strait, 

 Northwest Territories, June 25, L915. F. Johansen. 



Achorutes tullbergi Schaffer. 



Plate 1. figs. 1 10; plate 2, fig. 11. 



A chorutes dubius Tullberg, L876. -Uzel, 1890— Schott, 1894.4-Dalla Torre, 

 is'.':,. Schaffer, L896. -Skorikow, 1900. 



Achorutes dubius, var. concolor Carpenter, 1000. 



Achorutes tullbergi Schaffer. 1000a. 



Achorutes tullbergi, var. concolor Schaffer. L900a. — Wahlgren, 1907.— 

 Folsom, 1916. 



Pigmented with irregular patches of dark blue pigment (typical form) or 

 uniformly pigmented (var. concolor). Eyes (fig. 4) eight on each side. Postan- 

 nal organs (fig. I) with four (sometimes five) peripheral tubercles. Antennae 

 sh irter than the lead, with segments ; s 0:7:0:0 in relative lengths. Sense organ 

 of third antennal segment as in fig. 5. Ungues (fig. 6) stout, slightly Curving; 

 inner margin unidentate one third from apex. Unguiculi with setaceously 

 prolonged outer margin and with the basal lamella suboblong on the second and 

 third pairs of feet. Tenenl hairs knobbed; 2,3,3, as a rule: occasionally 3,3,3. 

 or 1,3,3. Mucrones figs. 7-9) one-third dentes in length, apically rounded, with 

 narrow outer lamella. Rami of tenaculum quadridentate. Anal spines (figs. 

 I (| . 11 [ two, half as long as hind ungues, arcuate, on prominent contiguous 

 papilla-. Clothing of spar-' short curving seta', with longer setae on the 

 p >sterior part of the abdomen. Length, - mm. 



The specimens collected by the Expedition belong to the variety concolor 



p., which has been taken hitherto in Franz Jcsef Land. Ellesmere land, 

 B (hernia and Massachusetts. The typical form of the species has been reported 

 from Nova Zembla, Spitzbergen and Siberia. 



ral specimens on ponds and from rotten driftwood. Bernard harbour, 

 Northwest Territories, May. 25, 1916, June is. 19, 1915; also several under 

 driftwood. Demarcation point, Alaska. May 16, 1914. F. Johansen. 



