Isotomidae of Japan and Asiatic part of Russia. II. The genus Tetracanthella of the Far East Potapov, Mikhail Brinev, Alexey Sun, Xin ZooKeys 2019 855 31 54 Martynova, 1977 in Martynova et al. 1977 1977 Collembola Isotomidae Tetracanthella CoL Animalia Tetracanthella orientalis Collembola 16 47 Arthropoda species orientalis   Material. Magadanskaya region: vicinities of Magadan, Snow Valley, 18.09.1974. It is the type locality of the species although the type specimens were not seen by us and are probably lost. Chukotski AO: Anadyrski district, vicinities of Anadyr, Observatsii Cape, tundra, 27.06.1974, leg. E. Bondarenko, Anadyrski district, Ugolnaya Bay, tundra, leg. M. Chernyakhovski. Kamchatka: Yuzhno-Kamchatski Reserve, Elizovski district (south), Kambalnoye Lake, pine elfin wood, 14.09.2005, leg. L. Lobkova; Elizovski district (north), Kronotski reserve, caldera of Uzon, moss-lichen tundra, 20.08.2005, leg. L. Lobkova; Kronotski reserve, Vachkazhets Volcano, 1000 ma lt., tundra, gopher burrow, leg. L. Lobkova; Bystrinski district, vicinities of Anavgai and Esso, 3-5.07.2012, tundra at lake (Ledum, Empetrum), leg. M.P.  Description. Body length 1.2-1.6 mm. Body slender, continuously narrowing (Fig. 40). Coloration dark, including antennae. Polygons large, canals between polygons well marked. Smooth fields usually present on all tergites of body (Fig. 49, 50). Posterior edge of head with smooth fields in lateral position (Fig. 50) or two groups of larger polygons (Fig. 57) in associated places. Area between ASi often with small smooth field. Dorsal mesochaetae short, slightly shortened in axial part of tergites (Fig. 49), in posterior row of Abd. IV not longer than on other parts of body (Md:p1 = 3.7-5.7). Abd. IV with p3 much longer than p1 (p3: p1 = 2.3-4.4). Macrochaetae long.  Figures 46-50. Tetracanthella tardokisp. nov. (46) and T. orientalis(47-50) 46-47 position of macrochaetae and s-chaetae on corpus 48 tenacular and furcal areas 49-50 dorsal chaetotaxy of Abd. II-V(49), head and Th.II (50), dorsal view. Abbreviations: fsc-a and fsc-p anterior and posterior furcal subcoxae, man manubrial field, ta tentacular area.  Figures 51-57. Reticulation of cuticle in Tetracanthellaof East Asia 51 T. annulatasp. nov., posterior edge of Abd.IV 52 T. sylvatica, ibidem 53 T. manschurica, posterior edge of Abd.IV, lateral part 54 T. czernovae, posterior edge of Abd.IV 55-56 T. tardokisp. nov., posterior edge of head (55) and posterior edge of Abd.IV (56) 57 T. orientalis, posterior edge of head. Abbreviations: p1 and p2, chaetae of p-row, sm-f smooth field. 8+8 ocelli, G and H reduced (dA: dH = ~1.5). PAO 2.5-4.0 as long as the diameter of ocellus A. Chaeta s'of ant.III in males present. Two prelabral chaetae. Outer maxillary lobe with three sublobal hairs and simple maxillary palp. Labium with three proximal and four basomedian chaetae, labial palp with reduced set of guards [A(1) B(3)C(0)D(3)E(4)] (as in Fig. 2). Postlabial chaetae 3+3. With 4-5 chaetae between medial line and pc3 on head. Frontal chaeta ap absent. Chaetotaxy scarce (Figs 49, 50). Axial chaetotaxy 12-10,8/4,4,4,4. Macrochaetotaxy: 3(W),3(W)/2,2,3. Mdl macrochaetae in p-row on Th. II and III, sometimes weakly developed. Number of s-chaetae: 3,3/2,2,2,2,4 (s), 1,0/1,0,0 (ms) (Fig. 47). S- chaetaeshort, medial ones on Abd. I-IIIarranged behind Mdl macrochaetae. Sternite of Th. III without chaeta. Legs as in T. tardokisp. nov. Tibiotarsi I, II, III with 21, 21, 22 chaetae. Claw without teeth. Empodial appendage short, 0.2-0.3 as long as inner edge of claw. Ventral tube with 3+3 lateral and four posterior chaetae. Retinaculum and furca absent. Retinacular field with 3-5 chaetae. Anterior furcal subcoxa with three (rarely four) chaetae, posterior one with four chaetae. Manubrial field with eight (rarely seven) chaetae (Fig. 48). Anal spines parallel, large, on high papillae. Papillae of inner pair sclerotised. Medial mesochaetae (a1) of Abd. V anterior to medial macrochaetae (a2) (Fig. 49). Arrangement of chaetae and spines on dorsum of Abd V as a2-a2/a1-a1 = 1.7-1.8; a2-a2/a2-eAS = 1.3-1.7. Males present.  Distribution.  Tetracanthella orientalisis widely distributed in northern part of the Far East of Russia (Fig. 58). In Magadanskaya region and Kamchatka it is the only known species of the genus. In Chukotka, T. orientaliscan be recorded together with T. sibiricawhich has the similar appearance but belongs to another group of species.  Figure 58. Records of five species of Tetracanthellain the Far East of Russia and Japan.  Discussion. See the remarks to T. tardokisp. nov.