COLLEMBOLA OF THE FAMILY ISOTOMIDAE 39 



Subgenus Ballistura Borner 

 BalUstura Borner, 1906, p. 172. 

 Subgenotype. — Isotoma schotti Dalla Torre. 



KEY TO SPECIES OF SUBGENUS BALLISTURA 



1. Dentes dorsally smooth. Eyes 16 2 



Denies with dorsal lobes. Eyes 12. Tenent hairs absent. Un- 



guiculus with an apical filament 3 



2. Dentes rounded apically. Tenent hairs absent. Postantennal 



organ slightly longer than the diameter of an adjacent eye. Un- 

 guiculus subulate apically. Dark violet, bluish, reddish, or 



brownish schotti (p. 39) 



Dentes not rounded apically. Tenent hairs present. Post- 

 antennal organ three times as long as the diameter of an ad- 

 jacent eye. Unguiculus not subulate. Bluish or grayish ewingi (p. 40) 



3. Dentes with several dorsal lobes. Fourth abdominal segment 



more than twice as long as the third. Antennae telescopic. 

 Apical filament of unguiculus short. Yellowish; the body 



segments bordered posteriorly with blackish excavata (p. 41) 



Dentes with about 10 dorsal lobes. Fourth abdominal segment 

 less than twice as long as the third. Antennae not telescopic. 

 Apical filament of unguiculus long, extending as far as the 

 unguis. Olive-green laticauda (p. 42) 



PROISOTOMA (BALLISTURA) SCHOTTI (Dalla Torre) 



Plate 12, Figures 120-125 



Isotoma litoralis Schott, 1894, p. 75. — Reuter, 1895, p. 29. 

 Isotoma schottii von Dalla Torre, 1895, p. 10.— Carpenter, 1900, p. 277. 

 Isotoma schotti Schaffer, 1896, p. 183; 1900a, p. 248.— Poppe and Schaffer, 1897, 

 p. 267.— Carpenter and Evans, 1899, p. 252.— Skorikow, 1900, p.^196.— 

 Borner, 1901a, p. 43.— Carl, 1901, p. 259.— Schott, 1902, p. 21.— Agren, 

 1903, p. 131.— Wahlgren, 1906b, p. 254. 

 Isotoma lacusiris Schott, 1896a, p. 185. 



Proisotoma schotti Linnaniemi (Axelson), 1907, p. 64; 1912, p. 123. — Collinge 

 and Shoebotham, 1910, p. 109.— Handschin, 1919, p. 76; 1924a, p. 

 Ill; 1929, p. 60.— Wahlgren, 1920, p. 8. — Carpenter and Phillips, 

 1922, p. 18.— Denis, 1924b, p. 228. 



Description. — Color variable; commonly dark violet or dark blue; 

 sometimes more or less reddish or brownish; intersegmental regions 

 appearing as pale bands. Antennal segments blue apically or blue 

 throughout; legs unpigmented beyond coxae; furcula unpigmented; 

 prothorax pigmented. Body short and stout. Eye spots half-moon 

 shaped, more posterior than is usual in the genus. Eyes eight on 

 each side, equal. Postantennal organ broadly elhptical, slightly 

 longer than the diameter of an eye, situated far from the eyes and 

 close to the antennal base. Antennae a Uttle shorter than the head, 

 with segments in relative lengths about as 4:7:8:10. Sense organ 

 of third antennal segment with two curving rods protected by an 

 integumentary fold. Special olfactory setae absent on the fourth 



