COLLEMBOLA OF THE FAMILY ISOTOMIDAE 103 



/. violacea is found under loose bark, on the ground under dead 

 leaves, logs, and stones, and in moss. It is one of the species that 

 occur in winter on the snow. 



Distribution. — The species has been recorded from Norway, Sweden, 

 Denmark, Finland, Russia, Spitsbergen, Siberia, Poland, Germany, 

 S\\itzerland, England, and Greenland. 



Canada: Arnprior, Ontario, November, January, C. Macnamara. 

 Greenland: Umanak, July 22, in moss, W. E. Ekblaw (American Museum of 

 Natural History, University of Illinois). 



ISOTOMA (ISOTOMA) VIOLACEA Tullberg variety MUCRONATA Axelson 



Plate 33, Figure 389; Plate 34, Figures 390-396 



Isotoma violacea var. mucronata Axelson, 1900, p. 118. — Wahlgrek, 1906b, p. 

 257. — Linnaniemi (Axelson), 1912, p. 158. — Folsom, 1919b, p. 281. — 

 Handschin, 1924a, p. 116; 1924b, p. 85.— Remy, 1928, p. 64. 



Isotoma mucronata Axelson, 1904, p. 72; 1905b, p. 33; 1906, p. 15. — Linnaniemi 

 (Axelson), 1907, p. 30; 1909, p. 12; 1911, p. 17.— Agren, 1904, p. 15. 



Description. — Clear blue to blackish violet; legs and furcula blue, 

 usually paler than the body. Anterior borders of body segments 

 often unpigmented, giving the effect of narrow pale bands. Apical 

 tooth of mucro the largest. Body setae exceptionally long and out- 

 standing; the largest setae sparsely feathered (pi. 33, fig. 389). Max- 

 imum length, 3.1 mm. 



According to Axelson, the two inner proximal eyes on each side are 

 smaller than the others; the postantennal organ is small, elliptical, 

 and scarcely as long as the diameter of one of the large eyes; the 

 lateral teeth and inner tooth of the unguis, and the angle-tooth of the 

 unguiculus, are strong (pi. 34, fig. 391). 



In specimens from Greenland that I studied (Folsom, 1919b) the 

 inner tooth of the unguis was absent (pi. 34, fig. 392). In a few of 

 these specimens the mucrones were abnormal in having only three 

 teeth (pi. 34, fig. 393). In some instances the subapical seta of the 

 dens extended beyond the middle of the mucro. Length, 1.3 mm. 



In specimens from Alaska all the teeth of the claws were well 

 developed; the subapical seta of the dens extended often beyond the 

 mucro; the tenaculum had 14 setae; and the ratio between the length 

 of the postantennal organ and the diameter of a large eye was as 

 11:12. Length, 2.6 mm. These Alaska specimens were more nearly 

 typical than those from Greenland. 



Remarks. — Variety mucronata occurs in the same situations as 

 typical violacea. My Greenland examples were taken in moss. The 

 Alaska specimens, five in number, were found in the nest of the 

 Aleutian rosy finch (Leucosticte griseonucha) . 



Distribution. — This variety has already been recorded from Norway, 

 Sweden, Finland, Switzerland, and Greenland. 



