COLLEMBOLA OF THE FAMILY ISOTOMIDAE 111 



sally, with a distal bristle extending beyond the mucro. Miicro 

 (pi. 38, fig. 437) falcately and subeqiially tridentate; second and 

 third teeth opposite each other. Kami of tenaculmn quadridentate 

 (pi. 38, fig. 438); corpus with numerous ventral setae. Clothing 

 (pi. 38, fig. 439) of dense simple or feebly serrate setae; with long 

 outstanding unilaterally fringed sensory setae. Maximum length, 

 6 mm. 



Remarks.— l>ioTth. American specimens of this well-loiown species 

 agree with the European examples that I have received. 



Having examined Packard's types in the Museum of Comparative 

 Zoology, Cambridge, Mass., I agree with MacGillivray (1896) that 

 Isotoma belfragei, purpurascens, plumbea, and the Massachusetts 

 specimens of tricolor, all belong to viridis Bourlet. The Texas speci- 

 mens, for which MacGillivray retained the name of tricolor, are 

 palustris Miiller. 



Isotoma capitola MacGillivray is synonymous with viridis Bourlet, 

 as I have found from a cotype given to me by MacGillivray. 



The form referred by MacGillivray to glavca Packard is also 

 viridis Bourlet, and is specifically distinct from Packard's glauca. 



Isotoma viridis is one of the most abundant collembolans, is the 

 largest known species of its genus in North America and Europe, 

 and may easily be recognized with the naked eye. It belongs pri- 

 marily to the fauna of the humus, and occurs in almost any soil 

 that is not too dry — in grass lands, woods, swamps, or cultivated 

 fields — congregating under stones, pieces of wood, dead leaves, or 

 other protection, and in piles of garbage or manure. It occurs in 

 moss, on pools of water, on the seashore under driftwood or seaweed, 

 and in winter on the snow. 



In the vicinity of Boston, Mass., I found full-grown specimens of 

 this species practically throughout the year. One individual laid 

 eggs on April 2. Minute specimens, recently hatched, were collected 

 on January 16, March 2, 10, 11, June 8, and October 2. 



Distribution. — The typical form of Isotoma viridis ranges through- 

 out Europe and North America and is known from Mesopotamia and 

 Mexico also. It has been reported from the following Arctic locali- 

 ties: Northern Siberia, Nova Zembla, Spitsbergen, Bear Island, Jan 

 Mayen, Iceland, Greenland, Northwest Territories, and Alaska. 



Maine: Orono, April 20, F. L. Harvey. 



New Hampshire: Mount Washington, Mrs. A. T. Slosson (Cornell UniversitjO- 

 Massachusetts: Arlington, January 16, March 1, 2, 4, 10, 11, 15, 18, 28, April 

 2, 8, 12, Mav 1, 10, 5, July 30. Beverly, A. P. Morse (Cornell University). 

 Cambridge, February 25, 28, March 2, 11, 15, 18, 28, April 22, May 7, 

 June 1, 8, 10, 16, 17, July 7, 16, October 2, 9. Chelsea, C. A. Walker 

 (Museum of Comparative Zoology). Salem, November 10-24, A. S. Packard 

 (Museum of Comparative Zoology). Waltham, July 29. 



