108 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



Remarks. — The cotypes of this species were taken on snow by 

 R. McCain, who wrote regarding them: "On a walk a mile or two 

 east of the city I saw some tree sparrows feeding quite extensively 

 on the snow. I was very puzzled as to the nature of this food that 

 they were finding so plentifully, but after repeated examinations of 

 the snow on which I saw them feeding, I found the rather wet snow 

 to be quite alive with snow fleas." 



Cotypes. — U.S.N.M. no. 42973, taken at Ann Arbor, Mich., 

 February 24, by R. McCain. 



ISOTOMA aSOTOMA) GKANDICEPS Reuter 



Plate 36, Figures 422-427 



Isotoma grandiceps Reuter, 1891, p. 229. — Schott, 1894, p. 71. — Schaffer, 

 1896. p. 179; 1900a, p. 247.— Scherbakov, 1898b, p. 9.— Carl, 1899, p. 302.— 

 AxELSON, 1903b, p. 7. 



Isotoma macnamarai Folsom, 1918, p. 291. 



Description. — Olive-green usually, sometimes blue. Antennae, legs, 

 and furcula pale green. Body segments bordered narrowly with 

 black (North American specimens). Head conspicuously large in 

 proportion to the body, almost as wide as the broadest part of the 

 abdomen, and as long as the thorax. Eyes (pi. 36, fig. 422) eight on 

 each side, on black patches. Postantennal organ (pi. 36, fig. 423) 

 lateral in position, close to the antennal base, elliptical, with very 

 thick wall, and a little longer than the diameter of one of the adjacent 

 eyes. Antennal base well developed. Antennae four-fifths as long 

 as the head, often arcuate, with segments variable in relative lengths 

 but about as 10:12:12:18-24. Sense organ of third antennal segment 

 (pi. 36, fig. 424) with two geniculate sense clubs. Fourth antennal 

 segment elliptical, without special olfactory setae. Third and fourth 

 abdominal segments subequal in length. Genital and anal segments 

 not clearly ankylosed. Tibiotarsus without a distal subsegment. 

 Unguis (pi. 36, fig. 425) exceptionally stout, with a pair of large 

 lateral teeth, and a conspicuous inner tooth one-tliird from the base. 

 Unguiculus more than half as long as the unguis, broadly lanceolate, 

 unidentate at the middle of the inner margin. Tenent hairs absent, 

 represented by a long simple hair. Furcula appended to the fifth 

 abdominal segment, gradually tapering and rather short, extending a 

 little beyond the posterior margin of the second abdominal segment. 

 Manubrium shorter than dentes, with many dorsal and ventral setae. 

 Dentes crenulate dorsally, with about five pairs of long stiff dorsal 

 setae and many stiff ventral setae. Mucrones (pi. 36, fig. 426) two- 

 fifths as long as hind ungues, quadridentate ; apical tooth short, almost 

 straight; second and third teeth large, subequal; fourth small, lateral, 

 at base of tliird. Rami of tenaculum quadridentate; corpus with 

 about eight setae. Clothing (pi. 36, fig. 427) of abundant strong 

 curving simple setae of moderate length, with long, outstanding. 



