COLLEMBOLA OF THE FAMILY ISOTOMIDAE 101 



inward, in size variable ; apical tooth usually long and slender. Post- 

 antennal organ up to three times as long as the diameter of an eye. 

 Unguis usually with a small inner tooth. Length, 2 mm (Linnaniemi). 



The specimens that I refer to this variety are pale yellow, in alcohol, 

 pigmented dorsally with a fine black network, the hypodermal nuclei 

 being indicated by pale spots. Mesonotum, metanotum, and abdom- 

 inal segments narrowly bordered posteriorly with black. Antennae 

 white; legs unpigmented, except coxae; manubrium pigmented, 

 dentes wliite. Head in large individuals with a dorsal interocular 

 network of pigment. Postantennal organ (pi. 33, figs. 376, 377) 

 narrowly elliptical, tliree to four times as long as the diameter of an 

 eye, with or without an anterior notch. Unguis (pi. 33, fig. 379) 

 with a pair of lateral teeth and an inner tooth. Unguiculus with a 

 conspicuous tooth. Maximum length, 1.8 mm. 



My specimens differ in coloration from grisescens, of wliich I 

 have European examples from Linnaniemi. Structurally they agree 

 in detail with olivacea, except for a constant and puzzhng variation 

 in the form of the mucrones. Li large, heavily pigmented individuals 

 the mucro is quadridentate (pi. 33, figs. 380, 381) but the apical 

 tooth is short — unlike that of typical grisescens. In small, Hghtly 

 pigmented individuals, however, the mucro has usually a long apical 

 tooth, as in grisescens, but the mucro is only tridentate (pi, 33, fig. 

 382), the lateral (fourth) tooth being present but the third tooth 

 being absent or else being present in the form of a minute rounded 

 lobe (pi. 33, fig. 383). 



Discussions of the synonymy are given by Linnaniemi (1912) and 

 Stach (1922a). I have adopted Stach's opinion in regard to the 

 priority of the name grisea Lubbock. 



Distribution. — This variety occurs in damp humus under dead leaves 

 or wood; also under manure, in moss, and sometimes on fungi. It 

 is known from Finland, Russia, Germany, Switzerland, Hungary, 

 England, and Scotland. 



Illinois: Urbana, May, in humus in woods (thousands collected with a Berlese 

 apparatus). 



ISOTOMA (ISOTOMA) VIOLACEA TuUberg 



Platk 33, Figures 384-388 



Isotoma violacea Tullberg, 1876, p. 36. — Schott, 1894, p. 69; 1902, p. 24; 

 1923, p. 12.— Reuter, 1895, p. 27.— Lie-Pettersen, 1896, p. 17.— Schaf- 

 FER, 1896, p. 187; 1900a, p. 246; 1900b, p. 258.— Poppe and Schaffer, 

 1897, p. 268.— Scherbakov, 1898b, p. 9.— Skorikow, 1900, p. 206.— Borner, 

 1901a, p. 57.— Becker, 1902, p. 28.— Agren, 1903, p. 136; 1904, p. 15.— 

 AxELSON, 1904, p. 72; 1905b, p. 33; 1906, p. 15.— Schille, 1906, p. 8.— 

 Wahlgren, 1906a, p. 224; 1906b, p. 257; 1919, p. 746.— Linnaniemi 

 (Axelson), 1909, p. 12; 1911, p. 17; 1912, p. 157.— Shoebotham, 1911, 

 p. 34.— Bartholin, 1916, p. 169.— Folsom, 1919b, p. 280.— Remy, 1928, 

 p. 64.— Handschin, 1928c, p. 128; 1929, p. 69. 



