COLLEMBOLA OF THE FAMILY ISOTOMIDAE 95 



doubly fringed setae (pi. 40, fig. 352) occur on the body segments, 

 becoming longer and stronger toward the extremity of the abdomen, 

 and being numerous on the last three abdominal segments. Several 

 such setae occur also on the bases of the legs, the number varying 

 somewhat. Length, 0.8 mm. 



Remarks.- — My material of this well-marked species agrees with 

 European descriptions of minor Schaffer and with five specimens 

 sent to me from Finland by Linnaniemi. The peculiar expanded 

 sensory setae of the fourth antennal segment are bluntly conical, as 

 in plate 30, figure 347, not only in individuals from Illinois but also 

 in those from Finland; they are represented as clavate by Borner 

 (1901) and by Linnaniemi (1912). My specimens had been treated 

 with potassium hydroxide. 



Isotoma minor is a species of the soil. It occurs in the soil itself 

 or on the surface under damp stones, wood, or fallen leaves, some- 

 times under loose bark and often in moss. It has been taken on 

 the seashore under stones, w^ood, and seaweed, and in dwelling houses 

 and greenhouses under flowerpots. As Linnaniemi notes, this 

 species is frequent in occurrence but seldom taken in abundance, 

 as the individuals occur singly or in sparse numbers. It is conspic- 

 uously lively, leaping rapidly and repeatedly when disturbed. The 

 white color and small size render it difficult to detect. 



Distribution, — I. minor has been recorded from almost all parts of 

 Europe, and from Mexico. 



Massachusetts: Norwood, August 26. 



Illinois: Champaign, October 20, in soil among roots of red clover. Homer, 

 April 6, 13, May 13, 16. 



ISOTOMA (ISOTOMA) ALBELLA Packard 



Plate 31, Figures 353-361 



Isotoma albella Packard, 1873, p. 32. — MacGillivray, 1891, p. 273; 1896, p. 

 51.— Schaffer, 1900b, p. 256.— Axelson, 1905b, p. 33; 1906, p. 15.— 

 Linnaniemi (Axelson), 1907, p. 30; 1909, p. 11; 1911, p. 16; 1912, p. 155.— 

 Wahlgren, 1906b, p. 256.— Stach, 1921, p. 161.— Handschin, 1929, p. 70. 



Isotoma nivea Schaffer, 1896, p. 184. — Axelson, 1900, p. 114. — Schott, 1902, 

 p. 26. 



Description. — White throughout, or pigmented sparsely with black- 

 ish or grayish pomts or flecks, which may form broken outlines around 

 the hypodermal nuclei. An elongate species. Eye spots black, long 

 and narrow (pi. 31, fig. 353), about two and one-half to three times 

 as long as wide. Eyes (pi. 31, figs. 354, 355) eight on each side of 

 the head, subequal. Postantennal organ (pi. 31, figs. 354, 355) 

 broadly elliptical or subovate, one and one-half to tw^o times as long 

 as broad, and two to three times as long as the diameter of an adja- 

 cent eye. Antennae one and one-half to two times as long as the 

 head, with segments in relative lengths about as 15:20:18:33. 

 Sense organ of third antennal segment as in plate 31, figure 356. 



