THE CANADIAN ENTOMOLOGIST 291 



A NEW ISOTOMA OF THE SNOW FAUNA. 



BY J. W. FOLSOM, URBANA, ILLINOIS. 



This Canadian species of Isotoma is here described in order 

 that its name may be used in a forthcoming article on insects of 

 the snow by Mr. Charles Macnamara, after whom the new collem- 

 bolan is named. He writes: "This species seems to be confined 

 to wooded swamps; I have never seen it elsewhere; and it some- 

 times comes out on the snow in small numbers. This is the only 

 pugnacious springtail I have ever observed. It almost always 

 attacks an Achorutes put in the same vial with it and sometimes 

 kills it." 



Isotoma tnacnamarai, new species. 



Olive green. Legs and furcula pale. Body segments bord- 

 ered narrowly with black. Head conspicuously large in proportion 

 to the body (fig. 1). Eyes (fig. 2) 8+8, on black patches. Post- 

 antennal organs absent. Antenna? four-fifths as long as the head, 

 with segments in relative lengths as 8, 12, 13, 21; fourth segment 

 elliptical. Sense organ of third antennal segment with two genicu- 

 late sense clubs (fig. 3). Fourth antennal segment with slender 

 curving sense hairs. Unguis stout (fig. 4), with a proximal outer 

 pair of small teeth and with a conspicuous inner tooth one-third 

 from the base. Unguiculus more than half as long as unguis, 

 broadly lanceolate, unidentate at the middle of the inner margin. 

 Tenent hair single, unknobbed. Third and fourth abdominal 

 segments subequal in length. Fifth and sixth abdominal seg- 

 ments not ankylosed. Furcula apparently appended to the fifth 

 abdominal segment, gradually tapering and short, extending a 

 little beyond the posterior margin of the second abdominal seg- 

 ment. Manubrium and dentes subequal in length. Dentes 

 crenulate dorsally. Mucrones two-fifths' as long as hind ungues, 

 quadridentate (fig. 5); apical tooth short, not hooked; second and 

 third teeth large, subequal; fourth small, lateral, at base of third. 

 Rami of tenaculum quadridentate; corpus with ventral setae. 

 Clothing of abundant strong curving setae of moderate length 

 (fig. 6), with long, outstanding, simple sensory setae, of which 

 there are several pairs on the fourth and the fifth abdominal seg- 



September, 1918 



