APTERYGOTA IO3 



MACHILIS ARCTICA sp. nov. 

 (PI. V, figs. 6-10; PL VIII, figs. 57, 58.) 



Body (fig. 6) annulated with alternating bands of dark brown and 

 pale yellow. Head colored as represented in fig. 57. Eyes circu- 

 lar in outline, contiguous along one-fifth the inner margin, or for a 

 distance equal to about one-third the diameter of an eye. Antennae 

 one-quarter longer than the body ; hairs white ; the basal ring and the 

 following seven segments are, in relative lengths, as 5 : 25 : 10 : 7 : 3 : 4 : 

 2:4; basal ring (fig. 7) yellow, bordered with brown ; basal segment 

 cylindrical, twice as long as broad, brown ; remaining segments yel- 

 low, obscurely banded with brown. Maxillary palpi (fig. 8) seven- 

 jointed, as usual, with segments related as 4:5:5:8:8:7:6; first 

 segment constricted near the base, with a lateral finger-like process 

 and a globose apex ; remaining segments simple, cylindrical, yellow, 

 with the following brown markings (fig. 8) : A basal patch on segment 

 two, a distinct basal ring on segment four, a diffuse basal ring on seg- 

 ments five and six and a subapical pate" ' on segment five. Labial 

 palpi (fig. 9) with segments related as 3 :3 5 ; first segment brown, 

 clavate, with a short apical process ; second i How, cylindrical, three 

 times as long as it is broad ; third yellow, strongly clavate. Body 

 slender ; the relative lengths of the successive segments, measured along 

 the median dorsal line, are 9:18:10:10:9:7:9:10:11 :ii :il : 

 10:7; thorax feebly arched; coxas (fig. 10) brown; trochanter yel- 

 low ; femur brown, with yellow apex ; tibia brown ; tarsus brown, 

 basally and apically ; claws and cerci brown. Median cercus one- 

 quarter longer than the body, or nearly as long as the antennae ; lateral 

 cerci nearly one-third as long as the median cercus. From a perfect 

 specimen were taken the following measurements of relative lengths : 

 body, 8; antennte, 11 ; median cercus, 10; lateral cerci, 3. 



The scales are so variable in size and form as to be of no specific 

 value, at least in this species; the cuticular figures, however (fig. 58), 

 will assist in distinguishing this form. Length, 8 mm. 



Type. — Cat. No. 5433, U. S. Nat. Museum. 



Nine types : three, Muir Glacier ("hillside to right"), June 11, 

 1899 (No. (>'^')\ five, Popof Island, 1S99 (Nos. 59, 66) ; one, Sitka, 

 June, 1899 (No. 61). 



I have found no species to which M. arctica is closely allied. Its 

 most distinctive characters are the relative lengths of body, antennae 

 and cerci, the coloration of the head, form and position of the eyes 

 and the color and form of the antennal and palpal segments. 



