4 A Canadian Arctic Expedition, 1913-18 



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

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

 Furcula very long, extending 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 base, 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 lamellse, 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 are in two longitudinal series. 

 Integument tuberculate. Length, 1.3 mm. 



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 ssmi-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 species often appears in fresh- 

 water aquaria, and is €^sentially 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 Arnprior, Ont., May 19, 1917, 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, 1915. F. Johansen. 



Achorutes tuUbergi Schaffer. 



Plate 1, figs. 4-10; plate 2, fig. 11. 



Achorutes dubius Tullberg, 1876.— Uzel, 1890.— Schott, 1894.— Dalla Torre, 

 1895.— Schaffer, 1896.— Skorikow, 1900. 



Achorutes dubius, var. concolor Carpenter; 1900. 



Achorutes tuUbergi Schaffer, 1900a. 



Achorutes tullbergi, var. concolor Schaffer, 1900a. — 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- 

 tennal organs (fig. 4) with four (sometimes five) peripheral tubercles. Antennse 

 shorter than the head, with segments as 6:7:9:9 in relative lengths. Sense organ 

 of third antennal segment as in fig. 5. Ungues (fig. 6) stout, sli_ghtly 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. Tenent 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 oiiter lamella. Rami of tenaculum quadridentate. Anal spines (figs. 

 10, 11) two, half as long as hind ungues, arcuate, on prominent contiguous 

 papillse. Clothing of sparse short curving setae, with longer setae on the 

 posterior part of the abdomen. Length, 2 mm. 



The specimens collected by the Expedition belong to the variety concolor 

 Carp., which has been taken hitherto in Franz Josef Land, Ellesmere land, 

 Bohemia and Massachusetts. The typical form of the species has been reported 

 from Nova Zembla, Spitzbergen and Siberia. 



Several specimens on ponds and from rotten driftwood, Bernard harbour, 

 Northwest Territories, May, 25, 1916, June 18, 19, 1915; also several under 

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



