Collemhola 11a 
Isotoma viridis var. riparia Nicolet. 
Desoria riparia Nicolet, 1841. — Gervais, 1844. 
Isoioma riparia Nicolet, 1847. 
Isotoma palustris var. riparia Tullberg, 1871. 
Isotoma palustris Tullberg, 1872 (part). 
Isotoma viridis var. aquatilis Schott, 1891. 
Isotoma viridis var. riparia Schott, 1894, 1896, 1902.^Dalla Torre, 1895. — 
Reuter, 1895.— Schaffer, 1896, 1900a.— Poppe and Schaffer, 1897.— Lie-Petter- 
sen, 1898.— Scherbakov, 1898a, 1898b.— Carl, 1899.— Wahlgren, 1899a, 1906a, 
1906b.— Absolon, 1900.— Bonier, 1901a.— Voigts, 1902.— Agren, 1903, 1904.— 
Axelson, 1903, 1905a, 1906.— (Axelson) Linnaniemi, 1907, 1909, 1911, 1912. 
Ground colour yellowish, greenish or brownish. The principal charac- 
teristic of this variety is a dark blue or blackish median dorsal stripe. Dark 
spots on the sides of the body segments may or may not be present. Maximum 
length, 5 mm. 
The specimens of /. viridis riparia collected by the Expedition are yellowish 
or greenish, pale ventrally, with or without the lateral dark spots and with the 
median stripe complete, or fading out posteriorly. Length, 2.5 mm. 
This variety prefers humid situations, and is found under damp wood, in 
moss, on the surface of fresh water, along the shores of ponds or streams and on 
the seashore under seaweed, driftwood or stones. 
The variety riparia ranges over north and middle Europe, and has been 
recorded from Arctic Siberia. 
In Canada, Mr. Charles Macnamara has taken this variety at Arn prior, 
Ont., in March and April. 
In the United States, the variety is known to me from New Hampshire, 
New York, Virginia, and Texas, at present. 
A few specimens under loose stones, Bernard harbour. Northwest Terri- 
tories, May, 1915. F. Johansen. 
Isotoma palustris (Miiller). 
Plate 6, figs. 53-57. 
Podura palustris Miiller, 1776.— Gmelin, 1778-93.— Bourlet, 1843. 
Isotoma palustris Lubbock, 1873.— Reuter, 1876 (part), 1890, 1891, 1895.— 
Reuter, L. and O. M., 1880.— Tomosvary, 1882.— Parona, 1885, 1895.— Oude- 
mans, 1888.— Dalla Torre, 1888, 1895.— Uzel, 1890, 1891.— Parfitt, 1891.— 
Schott, 1891, 1894, 1896, 1902.— Lie-Pettersen, 1896, 1898, 1907.— MacGillivray, 
1896.— Schaffer, 1896, 1898, 1900a, 1900b.— Poppe and Schaffer, 1897.— 
Scherbakov, 1898a.— Carl, 1899, 1901.— Carpenter and Evans, 1899.— Absolon, 
1900.— Borner, 1901a, 1902.— Krausbauer, 1902.— Agren, 1903.— Guthrie, 1903. 
Wahlgren, 1906b, 1907.— Collinge, 1910.— Collinge and Shoebotham, 1910.— 
Shoebotham, 1914. 
Isotoma tricolor Packard, 1873 (part). — rMacGillivray, 1891 (part), 1896. 
Isotoma aquatilis Lubbock, 1873 (part). — Parona, 1883. 
Isotoma Stuxbergii Tullberg, 1876 (part). 
Isotoma Tullbergi Moniez, 1889. 
Isotoma Stuxbergi Moniez, 1891. 
Isotoma aequalis MacGilliyray, 1896. 
Isotomurus palustris Borner, 1903, 1906. — Axelson, 1905a, 1906. — ^(Axelson) 
IJnnaniemi, 1911, 1912.— Imms, 1912. 
Very variable in colouration. The typical form is yellowish or greenish 
with blue, purple or blackish pigment; having a median dorsal stripe with 
irregular margins; and frequently lateral spots, which may coalesce to form a 
stripe on each side of the body. Head often with a dorsal lunate or anchor- 
