COLLEMBOLA OF THE FAMILY ISOTOMIDAE 25 



1900b, p. 5; 1906a, p. 222; 1906b, p. 255. — Absolon, 1900a, p. 28.— Skorikow, 

 1900, p. 206. — BoRNER, 1901a, p. 45. — Becker, 1902, p. 27.— Kratjsbauer, 

 1902, p. 42.— Agren, 1903, p. 143; 1904, p. 21.— Guthrie, 1903, p. 65.— 

 Axelson, 1904, p. 69; 1905a, p. 791; 1906, p. 12.— Evans, 1908, p. 199. 



Isotoma {Folsomia) quadrioculata Axelson, 1905b, p. 29. 



Folsomia quadrioculata Linn aniemi (Axelson), 1907, p. 21; 1909, p. 13; 1911, 

 p. 12; 1912, p. 111. — Bagnall, 1909, p. 500. — Collinge and Shoebotham, 

 1910, p. 110.— Bartholin, 1916, p. 168.— Shoebotham, 1917, p. 221.— 

 Brown, 1918, p. 186; 1919, p. 64.— Folsom, 1919a, p. 8.— Wahlgren, 1919, 

 p. 745.— Denis, 1921, p. 125; 1927, p. 192.— Stach, 1921, p. 160.— Carpen- 

 ter and Phillips, 1922, p. 14.— Schott, 1923, p. 10. — Handschin, 1924a, 

 p. 110; 1924b, p. 85; 1926, p. 125; 1928c, p. 127; 1929, p. 58.— Womersley, 

 1924a, p. 33; 1924b, p. 169; 1925, p. 219; 1927, p. 377.— Remy, 1928, p. 66. 



Description.— Dirty pale gray to grayish black, pigmented with 

 blackish spots, irregular in their form, size, and distribution. Small 

 specimens may be white, or white with scattered spots of grayish 

 blue. Large specimens are often blackish, mottled with white (unpig- 

 mented) spots; pale across the intersegmental regions; unpigmented 

 ventrally; with antennae, legs, and manubrium pigmented. In small 

 specimens the appendages are white, or pigmented basally. Eyes 

 (pi. 5, fig. 52) two on each side, one behind the other, each on its own 

 pigment spot, the posterior eye being the smaller. Postantennal 

 organ (pi. 5, fig. 52) long, narrow, with parallel sides, feebly curving, 

 three to four times as long as the diameter of the adjacent eye. 

 Antennae varying from a little shorter to a little longer than the head; 

 first segment about half as long as the second; second a little longer 

 than the third ; fourth two to three times as long as the first ; antennal 

 formula about 20:38:35:62. Sense organ of third antennal segment 

 as in plate 5, figure 53. Fourth antennal segment with terminal 

 tubercle, subapical papilla, and slender curving olfactory setae. 

 Antennal base well developed. Body stout. Fourth, fifth, and 

 sixth abdominal segments ankylosed; with a trace of a dorsal suture 

 between the fourth and fifth. Anus ventrocaudal. Tibiotarsal sub- 

 segment absent. Unguis (pi. 5, fig. 54) curving, simple, without 

 teeth. Unguiculus small, extending about half as far as the unguis 

 on the third pair of feet; one-third as far on the first and second pairs; 

 lanceolate, pointed, untoothed. Tenent hairs absent. Furcula 

 appended to the fourth abdominal segment, short, not quite attaining 

 the posterior margin of the second abdominal segment. Manu- 

 brium: dens: macro about as 5:3:1. Manubrium (pi. 5, fig. 55) with 

 two pairs of ventroapical strong chitinous hooks between the bases of 

 the dentes, and two pairs of ventral subapical setae. Dentes (pi. 5, 

 fig. 56) stout, not tapering greatly, with a few crenulations near the 

 middle of the dorsal region. Mucrones (pi. 5, figs. 56, 57) bidentate; 

 apical tooth more or less hooked; second tooth usually larger than the 

 first, erect or curving slightly forward. Rami of tenaculum quadri- 

 dentate; corpus with a single stout curving seta. Clothing (pi. 5, fig. 



