COLLEMBOLA OF THE FAMILY ISOTOMIDAE 105 



ISOTOMA aSOTOMA) NIGRIFRONS. new species 



Plate 35, Figures 404-411 



Description. — Pigment purple. In moderately pigmented individ- 

 uals the front is covered with a large blackish patch that includes the 

 antenna! bases, connects the eye spots anteriorly, and extends back- 

 ward between the eyes as a triangular mark, at the apex of which there 

 is a median transverse irregular black mark, or two such marks, one 

 in front of the other. Occiput whitish. Usually the first four body 

 segments are pigmented throughout, and the second, third, and fourth 

 abdominal segments have each a broad white posterior band. Often 

 the thorax is heavily pigmented with purple, while the posterior part 

 of the abdomen is paler in color. Antennae purplish throughout, or 

 with the first three segments whitish except apically. Legs purple 

 basally; beyond the coxae, whitish tinged with brownish or greenish; 

 apices of tibiotarsi purple. Furcida white. Eyes (pi. 35, fig. 404) 

 eight on each side, the two inner proximal eyes smaller than the others. 

 Postantennal organ (pi. 35, figs. 404, 405) elHptical, from one-fourth 

 longer to twice as long as the diameter of the adjacent eye. Antennal 

 bases well developed. Antennae longer than the head (as 7:5), with 

 segments in relative lengths about as 12:25:23:36. Sense organ of 

 tliird antennal segment (pi. 35, fig. 406) with a pair of hnear curving 

 rods and a chitinous ridge. Fourth antennal segment without special 

 olfactory setae. Third abdominal segment slightly longer than the 

 fourth. Genital and anal segments not clearly ankylosed, though 

 the dorsal suture is sometimes faint. Unguis (pi. 35, fig. 407) with a 

 pair of lateral teeth and an evident tooth at the middle of the inner 

 margin. Unguiculus lanceolate, acuminate, strongly unidentate, 

 extending about half as far as the unguis on the second and third 

 pairs of feet, and less than half as far on the first pair. Tenent hairs 

 absent. Furcula extending not quite to the ventral tube. Manu- 

 brium with many stiff setae dorsally and ventrally. Dens twice as 

 long as manubrium, slender, tapering, with many stiff setae laterally 

 and ventrally, crenulate dorsally, the crenulations ending distally 

 before the apex, leaving a smooth surface three times as long as the 

 mucro. Mucro (pi. 35, figs. 408-411) half as long as liind unguiculus, 

 quadridentate ; apical tooth large, hooked; anteapical tooth large, 

 subconical, erect; third and fourth teeth small, subequal, erect or 

 oblique, almost opposite each other; fourth tooth lateral. Rami of 

 tenaculum quadridentate; corpus with about 12 setae (1 1-13). Cloth- 

 ing of dense simple setae of moderate length, longer posteriorly; 

 sensory setae long, outstanding, simple. Maximum length, 2.1 mm. 



Remarks. — /. nigrifrons is close to olivacea Tullberg, from which, 

 however, it differs strikingly in coloration. Structurally this species 

 differs from olivacea chiefly in having unequal eyes and relatively 

 shorter postantennal organs. 



