Holotype, female (No. FE-2011022-2) (SEM), Russia, Far East, Primorsky Krai, Khasansky area, eastern part of Krabbe Peninsula, from mixed samples of soil and moss under a broad-leaved forest on a hill beside the coast, 42°37.40'N, 130°52.35'E, 16-IX-2011, coll. Y. Bu, C. W. Huang, M. Potapov & V. Alpatov. Paratypes, 2 females (Nos. FE-2011022-1, FE-2011023) (SEM; MSPU), 1 maturus junior (No. FE-2011022-3) (SEM), same data as holotype.

Adult body length 1000–1100 µm (n=3), pale yellow in color (Fig. 3A).

Head (Fig. 2A). Ovate, length 90–110 µm, width 70 µm. Setae d6 present, sd4 and sd5 short sensilliform. Setae d6 11 µm, d7 10 µm and sd7 19 µm in length. Clypeal pore cp and frontal pore fp present. Pseudoculus round, length 7–8 µm, with short posterior extension, PR=15 (Fig. 2B). Calyx of maxillary gland smooth, without any appendix, blind end split into two leaves, posterior filament 15 µm, CF=7 (Fig. 2C). Maxillary palpus with two tapering sensilla, subequal in length (Fig. 2D). Labial palpus reduced, with three setae and one lanceolate basal sensillum (Fig. 2E).

Foretarsus (Fig. 2G, H). Length 80 µm, claw length 20 µm, without inner flap, TR=4; empodium length 3 µm, EU=0.15. Dorsal sensilla t-1 baculiform, t-2 slender and long (17 µm), BS=0.33, t-3 broad-leaf shape. All other exterior sensilla slender, except broadened sensillum g, a surpassing base of b and c, b broad at base and extremely long (29 µm), reaching base of γ4, c nearly reaching base of e and slightly lower than b and d, d located at same level to b, e short, f long, g broad and short. Interior sensilla a’ lanceolate and broad, b’ absent, c’ reaching base of claw. Relative length of sensilla: t1 = t3 < a’ < (g = t2 = c’) < a < (c = e) < d < f < b. Setae β1 and δ4 sensillum, 6 µm and 7 µm respectively. Pores close to base of sensilla a and t3 present. Length of middle tarsus 35 µm, claw length 15 µm. Length of hind tarsus 38 µm, claw length 18 µm.

Thorax. Thoracic chaetotaxy given in Table 1. Setae 1 and 2 on pronotum 16 µm and 12 µm length respectively, mesonotum and metanotum with eight pairs of P-setae, accessory setae short sensilliform; setae P1, P1a and P2 on mesonotum 15 µm, 3 µm and 20 µm respectively (Fig. 2I). Prosternum with two pairs of anterior seta, and setae A2 and M2 sensilliform (Fig. 3B). Mesosternum and metasternum each with 7 A-setae, and setae A2 sensilliform (Fig. 3C, D). Pronotum and prosternum without pores (Figs 2I, 3B). Mesonotum with pores sl and al, metanotum with pores sl only (Fig. 2I). Mesosternum and metasternum without pores (Fig. 3C, D). Single membranal pore present on membrane between each coxa and the body.

Abdomen. Abdominal chaetotaxy given in Table 1. Tergite I with three pairs of anterior setae (A1, A2, A5) and six pairs of posterior setae (Fig. 2K). Tergites II–VI with eight pairs of posterior setae. Tergite VI and VII with four pairs of anterior setae (A1, A2, A4, A5). Tergites VII with nine pairs of posterior setae, P3a present. All accessory setae on tergites I–VII sensilliform, 5–6 µm on tergites I–VI and 7 µm on VII. Tergite VIII with paired setae M1 (Fig. 3G). Sternite IV–VII each with eight posterior setae, Pc absent (Fig. 3H, I, J). Sternite VIII with 4 setae.

Tergites I and VIII with pores psm only (Figs 2K, 3G), II–V with pores psm and al (Fig. 3E), VI–VII with pores psm, al and psl (Fig. 3F), IX–XI without pores, XII with single medial pore. Sternites I–III without pores, IV with 1+1 anteromembranal pores, V and VI each with 1+1 posterior pores anterior to seta P1 and 1+1 anteromembranal pores (Fig. 3H, I), VII with single posterior pore asymmetrical located left or right and 1+1 anteromembranal pores (Fig. 3J), VIII–XI without pores, XII with 1+1 pores al.

Abdominal appendages I, II, III with 2, 1, 1 segments and 4, 2, 2 setae respectively. On appendages II and III, subapical seta 15–17 µm, apical seta 11–12 µm in length. Striate band on abdominal segment VIII reduced, anterior margin regular wave shaped (Fig. 3G). Comb on abdomen VIII rectangular, with 12–13 teeth (Fig. 2J). Female squama genitalis with very short basal apodeme, extremely long and pointed acrostyli (Fig. 2F). Male unknown.

The species is named after Krabbe Peninsula where the type specimens were collected.

Known only from type locality.

Baculentulus krabbensis sp. n. is characterized by extremely long sensilum b on foretarsus, sensillum a’ located distal to t1, sensillum b’ absent, eight A-setae on tergite VI and VII, presence of P3a on tergite VII, and special female genitalia with short basal apodeme.

We placed the present new species in the genus Baculentulus because the baculiform sensillum t1 on foretarsus, reduced labial palpus with three setae and one sensillum, smooth calyx of maxillary gland, reduced striate band, two pairs of anterior setae on mesonotum and metanotum, abdominal appendages II and III each with two setae of different length, and only 4 setae on sternite VIII. It is similar to Baculentulus samchonri (Imadaté & Szeptycki, 1976) from North Korea in having eight A-setae on both tergites VI and VII, absence of sensillum b’ and extremely long sensillum b on foretarsus. They can be distinguished by the posterior setae on tergite VII (9 pairs of P-setae with P3a present in Baculentulus krabbensis sp. n. vs. 8 pairs of P-setae with P3a absent in Baculentulus samchonri), the anterior setae on tergite I (6 A-setae in Baculentulus krabbensis sp. n. vs. 4 in Baculentulus samchonri), the length of sensillum f (extremely long and surpassing the base of claw in Baculentulus krabbensis sp. n. vs. short and not reaching base of claw in Baculentulus samchonri), and the shape of female squama genitalis (basal apodeme very short in Baculentulus krabbensis sp. n. vs. basal apodeme in moderate length in Baculentulus samchonri).

Holotype, female (No. FE-2011051-2) (SEM), Russia, Far East, Primorsky Krai, Lazovsky area, nearby Preobrazheniye, from the mixed samples of humus (full of white mycelium) and a little soil under a broad-leaved forest close to the seashore, 42°54.16'N, 133°53.33'E, 22-IX-2011. coll. Y. Bu, C. W. Huang, M. Potapov & V. Alpatov. Paratypes, 5 females (Nos. FE-2011046-2, FE-2011052-4, FE-2011052-5, FE-2011052-6, FE-2011073-1) (SEM), 5 males (Nos. FE-2011071-1, FE-2011072-1, FE-2011074-1, FE-2011075-1, FE-211075-3) (SEM; MSPU), same data as holotype. Other materials, 3 male preimagos (Nos. FE-2011048-2, FE-2011048-3, FE-2011049-3) (SEM), same date as holotype.

Adult body length 1100–1300 µm (n=10), pale yellow in color (Fig. 5A).

Head (Fig. 4A). Ovate, length 120–125 µm, width 85 µm. Setae d6 present, sd4 and sd5 short sensilliform. Setae d6 and d7 subequal in length. Seta sd7 18 µm in length. Clypeal pore cp and frontal pore fp present. Pseudoculus round, length 9–10 µm, with short posterior extension, some irregular lines visible under light microscope, PR=12–13 (Fig. 4B). Calyx of maxillary gland smooth, with one helmet-like dorsal appendix, blind end split into two leaves, and posterior filament 15 µm, CF=8 (Fig. 4C). Maxillary palpus with two tapering sensilla, dorsal one (8–10 µm) slightly longer than lateral one (7–9 µm) (Fig. 4D). Labial palpus reduced, with two-branched terminal tuft of setae, with one leaf-shape basal sensillum (Figs 4E, 5B).

Foretarsus (Fig. 4H, I). Length 90–95 µm, claw length 20–21 µm, without inner flap, TR=4.3–4.7; empodium length 4 µm, EU=0.2. Dorsal sensilla t-1 claviform, t-2 slender and long (25–26 µm), BS=0.38–0.42, t-3 short and lanceolate. All other exterior sensilla slender, with except a slightly broad, surpassing base of c, b shorter than c and located in subequal level, d lower than c, e slender, f long, g short. Interior sensilla a’ short and broad, b’ slender and surpassing base of δ5, c’ reaching base of claw. Relative length of sensilla: t3 < t1< a’ < b < (a = g = d = b’ = c’) < (c = e = f = t2). Setae β1 and δ4 sensillum, 7 µm and 5 µm respectively. Pores close to base of sensilla a and t3 present. Length of middle tarsus 40–45 µm, claw length 18–20 µm. Length of hind tarsus 45–50 µm, claw length 20–23 µm.

Thorax. Thoracic chaetotaxy given in Table 2. Setae 1 and 2 on pronotum 20 µm and 15 µm length respectively, mesonotum and metanotum with eight pairs of P-setae, accessory setae short sensilliform, 2.5 µm; setae P1, P1a and P2 on mesonotum 18–20 µm, 2.5 µm and 22–25 µm respectively (Fig. 4J). Prosternum with two pairs of anterior seta, and setae A2 and M2 sensilliform (Fig. 5C). Mesosternum and metasternum each with 7 A-setae, and setae A2 and A4 sensilliform (Fig. 5D, E). Pronotum and prosternum without pores (Figs 4J, 5C). Mesonotum with pores sl and al, metanotum with pores sl only (Fig. 4J). Mesosternum and metasternum each with single median pore, situated anterioral to level of setae M (Fig. 5D, E).

Abdomen. Abdominal chaetotaxy given in Table 2. Tergite I with three pairs of anterior setae (A1, A2, A5) and six pairs of posterior setae. Tergites II–VI with eight pairs of posterior setae. Tergite VI and VII with four pairs of anterior setae (A1, A2, A4, A5). Tergite VII with nine pairs of posterior setae, P3a present. All accessory setae on tergites I–VII short sensilliform, 3 µm on tergites I–VI and 6 µm on VII. Tergite VIII with paired setae M1 (Fig. 5F). Sternites IV–VII each with eight posterior setae, Pc absent (Fig. 5K, L, M). Sternite VIII with two rows of setae (4/2) (Fig. 5G).

Tergites I and VIII with pores psm only, II–VII with pores psm and al, IX–XI without pores, XII with single medial pore (Fig. 5F). Sternites I–III without pores (Fig. 5H–J), IV with 1+1 anteromembranal pores (Fig. 5K, N), V and VI each with 1+1 posterior pores close to seta P1 and 2+2 anteromembranal pores (Fig. 5L, O, P), VII with single posterior pore asymmetrical located left or right (Fig. 5M), VIII–XI without pores, XII with 1+1 pores al.

Abdominal appendages I, II, III with 2, 1, 1 segments and 4, 3, 3 setae respectively. On appendages II and III, subapical seta 19–21 µm, two apical setae 11–12 µm, and 5–7 µm in length (Fig. 5I–J). Striate band on abdominal segment VIII reduced, anterior margin with sparse irregular teeth (Figs 4K, 5F, G). Comb on abdomen VIII rectangular, with 12 teeth (Fig. 4L). Female squama genitalis with short subuliform acrostyli (Fig. 4F). Male squama genitalis with 5+5 setae on dorsal side and 3+3 setae on ventral side (Fig. 4G).

Chaetal variability. Chaetal variations were observed in 4 specimens: on tergite VI, asymmetrical absence of A4 of right side (No. FE-2011071-1); on tergite VII, asymmetrical absence of P1 of right side (No. FE-2011052-4); on sternite VII, absence of Ac (No. FE-2011075-1), and asymmetrical absence of A2 of left side (No. FE-2011052-6).

The species is named after Lazovsky Nature Reserve where the type specimens were collected.

Known only from type locality.

Fjellbergella lazovskiensis sp. n. is characterized by three pairs of anterior setae on tergites II-V which is different to any other members of the genus, four pair of anterior setae, nine pairs of posterior setae on tergite VII, foretarsal sensilla b, c and d located in subequal level, b shorter than c, and tergite IX and X with 14, 12 setae respectively.

The present species is located in the genus Fjellbergella because three setae on abdominal legs, labial palpus with two-branched terminal tuft of setae, claviform sensillum t1 on foretarsus, reduced striate band, two pairs of anterior setae on mesonotum and metanotum, and 4/2 setae on sternite VIII. Fjellbergella lazovskiensis sp. n. is similar to Fjellbergella tuxeni Nosek, 1980 from Alaska in having 8 A-setae on tergite VII and presence of P1a on tergite I–VII. They can be distinguished by the chaetotaxy of tergite IX and X (14 and 12 setae in Fjellbergella lazovskiensis sp. n. respectively vs. 12 and 8 setae in Fjellbergella tuxeni), length and location of foretarsal sensilla b and c (b shorter than c and they located at the same level in Fjellbergella lazovskiensis sp. n. vs. b and c subequal in length and c located lower than b distinctly in Fjellbergella tuxeni), shape and length of sensillum a’ (broad and reaching base of sensillum b’ in Fjellbergella lazovskiensis sp. n. vs. slender and far surpassing base of sensillum b’ in Fjellbergella tuxeni), and shape of claw of foreleg (absence of inner flap in Fjellbergella lazovskiensis sp. n. vs. presence in Fjellbergella tuxeni). In addition, the new species has only 6 anterior setae on tergites II-V contrary to two other members of this genus, which have 8 anterior setae.

Holotype, female (No. FE-2011035-1) (SEM), Russia, Far East, Primorsky Krai, Lazovsky area, nearby Preobrazheniye, from the mixed samples of soil and humus from mountains, 42°54. 48'N, 133°53. 96'E, 21-IX-2011, coll. Y. Bu, C. W. Huang, M. Potapov & V. Alpatov. Paratypes, 1 female (No. FE-2011035-6), 3 males (Nos. FE-2011035-4, FE-2011037-1, FE-2011045-3) (SEM; MSPU), 2 male preimagos (Nos. FE-2011038-1, FE-2011038-2) (SEM), same data as holotype.

Adult body length 1200–1350 µm (n=5).

Head (Fig. 6A). Ovate, length 120–130 µm, width 70–80 µm. Setae d6 present, sd4 and sd5 short sensilliform. Setae d6 11 µm, d7 10 µm and sd7 18 µm in length. Clypeal pore cp and frontal pore fp present. Pseudoculus round, length 7–8 µm, with short posterior extension, PR=16 (Fig. 6B). Calyx of maxillary gland smooth, without any appendix, blind end split into two leaves, posterior filament 16–17 µm, CF=7–8 (Fig. 6C). Maxillary palpus with two tapering sensilla, dorsal snsillum is evidently longer than lateral one (Fig. 6D). Labial palpus completed, with one-branched terminal tuft of setae, with three setae and one lanceolate basal sensillum (Fig. 6E).

Foretarsus (Fig. 6G, H). Length 86–93 µm, claw length 20–23 µm, without inner flap, TR=4; empodium length 4 µm, EU=0.18. Dorsal sensilla t-1 baculiform, t-2 slender and long (23 µm), BS=0.5, t-3 lanceolate. Exterior sensilla a surpassing base of b and c, b slender and short (16 µm), not reaching base of γ3, c reaching base of f and in subequal level to b, d located higher than b and c, e long and reaching base of claw (30 µm), f slender, g broad and short (18 µm). Interior sensilla a’ broad, b’ slender and reaching base of α6, c’ nearly reaching base of claw. Relative length of sensilla: t3 < t1 < b < (a = a’) < g < (b’ = c’) < d < t2 < c < e < f. Setae β1 setiform and δ4 sensilliform. Pores close to sensilla a and t3 present. Length of middle tarsus 40 µm, claw length 17 µm. Length of hind tarsus 45 µm, claw length 20 µm.

Thorax. Thoracic chaetotaxy given in Table 3. Setae 1 and 2 on pronotum 20 µm and 12–14 µm length respectively. Mesonotum and metanotum with eight pairs of P-setae, accessory setae short sensilliform, 2 µm in length; setae P1, P1a and P2 on mesonotum 17–20 µm, 3 µm and 20–24 µm respectively. Prosternum with two pairs of anterior seta, and setae A2 and M2 sensilliform. Mesosternum and metasternum each with 7 A-setae, and setae A2 sensilliform. Pronotum and prosternum without pores. Mesonotum with pores sl and al, metanotum with pores sl only. Mesosternum and metasternum each with single median pore, situated anterioral to level of setae M.

Abdomen. Abdominal chaetotaxy given in Table 3. Tergite I with three pairs of anterior setae (A1, A2, A5). Tergites II–VI with eight pairs of posterior setae. Tergites VI and VII with four pairs of anterior setae (A1, A2, A4, A5). Tergite VII with nine pairs of posterior setae, P3a present. All accessory setae on tergites I–VII short sensilliform, 3 µm on tergites I–V, 4 µm on tergite VI, and 5 µm on VII. Tergite VIII with paired setae M1. Sternite IV–VII each with eight posterior setae, Pc absent. Sternite VIII with two rows of setae (4/2).

Tergites I and VIII with pores psm only, II–V with pores psm and al, VI–VII with pores psm, al and psl, IX–XI without pores, XII with single medial pore. Sternites I–IV without pores, V and VI each with 1+1 posterior pores anterior to seta P1 and 1+1 anteromembranal pores, VII with single posterior pore asymmetrical located left or right and 1+1 anteromembranal pores, VIII–XI without pores, XII with 1+1 pores al.

Abdominal appendages I, II, III with 2, 1, 1 segments and 4, 2, 2 setae respectively. On appendages II and III, subapical setae 16–17 µm, apical setae 13–14 µm in length. Striate band on abdominal segment VIII reduced, anterior margin regular wave shaped. Comb on abdomen VIII rectangular, with 12–13 teeth (Fig. 6I). Female squama genitalis robust, with moderate basal apodeme and pointed acrostyli (Fig. 6F). Male squama genitalis with 5+5 setae on dorsal side and 3+3 setae on ventral side (Fig. 6J).

The species is named after Dr. V. Alpatov who accompanied us during our scientific trips.

Known only from type locality.

Yichunentulus alpatovi sp. n. is characterized by the presence of sensillum b’ on foretarus and short sensilum b on foretarsus, 6 anterior seate on tergites IV–V, swelled sensillum a’, presence of pores psl only on tergites VI and VII, and female squama genitalis with moderate basal apodeme and pointed acrostyli.

The present species is located in the genus Yichunentulus because the labial palpus with one-branched terminal tuft of setae, with three setae and one lanceolate basal sensillum, the baculiform sensillum t1 on foretarus, reduced striate band, two pairs of anterior setae on mesonotum and metanotum, 4/2 setae on sternite VIII, and abdominal appendages II and III each with two setae of different length. Yichunentulus alpatovi sp. n. is close to the type species Yichunentulus yichunensis Yin, 1980 in having short sensillum b and identical body chaetotaxy. However, it can be easily distinguished from Yichunentulus yichunensis and Yichunentulus borealis (Nakamura, 2004), comb. n. by the presence of sensillum b’ on foretarsus. It also differs from Yichunentulus yichunensis in the length of sensillum e (extremely long in Yichunentulus alpatovi sp. n. vs. short in Yichunentulus yichunensis) and sensilla c’ (long and surpassing base of δ6 in Yichunentulus alpatovi sp. n. vs. short and only reaching base of β7 in Yichunentulus yichunensis). It differs from Yichunentulus borealis in the chaetotaxy of tergites IV–V (each with 6 A-setae in Yichunentulus alpatovi sp. n. vs. 8 in Yichunentulus borealis), shape of sensillum a’ (slightly broad and as long as sensillum a in Yichunentulus alpatovi sp. n. vs. distinctly swell and shorter than sensillum a in Yichunentulus borealis), and the body porotaxy (pore psl present on tergites VI and VII only and sternites I–IV without pores in Yichunentulus alpatovi sp. n. vs. psl present on tergites III–VII and sternites II and IV each with 1+1 anteromembranal pores in Yichunentulus borealis).

Yichunentulus yichunensis Yin, 1980.

Mesonotum and metanotum each with two pairs of anterior setae, abdominal appendages II and III each with two setae, labial palpus with one-branched terminal tuft of setae, with 3 setae and 1 sensillum, foretarsal sensillum t1 baculiform, sensillum b’ absent or present, sensillum a’ located distal to t1, maxillary gland simple and without appendages, sternite VIII with 4/2 setae, striate band on abdominal segment VIII reduced, and sternites II–VI each has 1+1 membranal pores.

The genus Yichunentulus Yin, 1980 has only one species described from Heilongjiang, Northeast China (Yin 1980). After compare Baculentulus borealis Nakamura, 2004 with congeners, we find two important characters of this species: presence of one-branched terminal tuft of setae and 3 seate on labial palpus and 4/2 setae on sternite VIII are different to any other species of the genus Baculentulus. On the contrary, those two characters match well with genus Yichunentulus. Two specimens of Baculentulus borealis newly collected from type locality are also studied. We proposed to transfer Baculentulus borealis to the genus Yichunentulus as a new combination Yichunentulus borealis (Nakamura, 2004), comb. n. The three species of the genus Yichunentulus can be distinguished by the following key.

1 female, 1 male, Locality 3, 25-IV-2010, coll. E. Sokolova & M. Potapov.

Russia (Far East, Khabarovsk Krai).

Body length 1300–1380 µm, foretarsus length 110 µm. We studied the new materials of Yichunentulus borealis collected from type locality and redescribe the head chaetotaxy and body porotaxy. Head with d6 seta present, sd4 and sd5 sensilliform. Pronotum and prosternum without pores. Mesonotum with pores sl and al, metanotum with pores sl only. Mesosternum and metasternum each with single medial pore. Tergites I and VIII with pores psm only, II with pores psm and al, III–VII with pores psm, al and psl, IX–XI without pores, XII with single medial pore. Sternites I with single medial pore, II–IV without 1+1 anteromembranal pores, V and VI each with 1+1 posterior pores anterior to seta P1 and 1+1 anteromembranal pores, VII with single posterior pore asymmetrical located left or right, VIII–XI without pores, XII with 1+1 pores al.

7 females (Nos. FE-2011062-1, FE-2011062-4, FE-2011062-5, FE-2011085-1, FE-2011085-2, FE-2011087-1, FE-2011089-1) (SEM; MSPU), 5 males (Nos. FE-2011062-2, FE-2011062-3, FE-2011086-1, FE-2011086-2, FE-2011087-2) (SEM; MSPU), 1 male preimago (No. FE-2011090-2), Russia, Far East, Khabarovsk Krai, Vaninsky area, nearby Vysokogorny, Valley of Mulinka, from Picea and Abies forest on Northeast slope, sample No. 27, 750 m alt., 30-IX-2011, 1 male preimago (No. FE-2011059-2), 1 maturus junior (No. FE-2011059-1), Russia, Far East, Khabarovsk Krai, Vaninsky area, nearby Datta, from coastal larch-wood on East slope (green moss), sample No. 24, 28-IX-2011. 1 female (No. FE-2011060-1), Russia, Far East, Khabarovsk Krai, Vaninsky area, nearby Vysokogorny, Valley of Mulinka, from spruce forest at pass, sample No. 26, 900 m alt., 29-IX-2011. 2 females (FE-2011067-2, FE-2011088-1), 1male (No. FE-2011088-2), Russia, Far East, Khabarovsk Krai, Vaninsky area, nearby Vysokogorny, Valley of Mulinka, from mixed sample of spruce-forest and rotten wood, sample No. 30, 600 m alt., 29-ix-2011. 1 female (No. FE-2011069-1), Russia, Far East, Khabarovsk Krai, Vaninsky area, nearly Vysokogorny (5 km South), Valley of Dopolnitel’ny Stream, from mixed sample of litter under old poplar-trees in floodplain, sample No. 32, 400 m alt., 30-IX-2011. All specimens are collected by M. Potapov & V. Alpatov.

Adult body length 1000–1200 µm (n=16), yellow in color (Fig. 8A).

Head (Fig. 7A). Ovate, length 130–135 µm, width 80–85 µm. Setae d6 present, sd4 and sd5 short. Setae d6 14–15 µm, d7 16–17 µm and sd7 18–19 µm in length. Clypeal pore cp and frontal pore fp present. Pseudoculus round, length 7–8 µm, with short posterior extension, PR=16–17 (Fig. 7B). Maxillary gland large, calyx with lateral racemose appendices and one helmet-like dorsal appendix, and bilobed posterior dilation, posterior filament length 20–22 µm, CF=6–7 (Fig. 7C). Labial palpus reduced, with one-branched terminal tuft of setae, three setae and one leaf-shaped basal sensillum (Figs 7D, 8B), but well developed in five specimens (Figs 7E, 8C). Maxillary palpus with two tapering sensilla, subequal in length (Fig. 7F).

Foretarsus (Fig. 7H, I). Length 85–92 µm, claw length 23–29 µm, with one inner flap, TR=3.5–3.7; empodium length 4 µm, EU=0.15–0.18. Dorsal sensilla t-1 filiform, t-2 slender and long (17 µm), BS=0.33, t-3 lanceolate and short. All exterior sensilla slender, a far surpassing base of b and c, b slightly longer than c, c short and lower than b, d and e short, f long, g broad and short. Interior sensilla a’ broad and long, surpassing base of δ5, b’ absent, c’ slender and surpassing base of claw. Relative length of sensilla: t3 < g < t1 < (c = d = e) < b < a’ < a < t2 < c’ < f. Setae β1 and δ4 sensilliform, 12–13 µm in length. Pores close to sensilla c and t3 present. Length of middle tarsus 40 µm, claw length 15–20 µm. Length of hind tarsus 45 µm, claw length 18–20 µm.

Thorax. Thoracic chaetotaxy given in Table 4. Setae 1 and 2 on pronotum 26–35 µm and 16–17 µm length respectively, mesonotum and metanotum with eight pairs of P-setae, accessory setae sensilliform; setae P1, P1a and P2 on mesonotum 30 µm, 10 µm and 43 µm respectively (Fig. 7J). Prosternum with two pairs of anterior seta, and setae A2 and M2 sensilliform (Fig. 8E). Mesosternum with 5 A-setae, and metasternum each with 7 A-setae, and setae A2 sensilliform (Fig. 8F, G). Pronotum and prosternum without pores (Figs 7J, 8E). Mesonotum with pores sl and al, metanotum with pores sl only (Fig. 7J). Mesosternum and metasternum each with single medial pore (Fig. 8F, G). Single membranal pore present on membrane between each coxa and the body.

Abdomen. Abdominal chaetotaxy given in Table 4. Tergite I with three pairs of anterior setae (A1, A2, A5) and six pairs of posterior setae. Tergites II–VII with eight pairs of posterior setae, P3a present. Tergite VII with four pairs of anterior setae (A2, A3, A4, A5). Tergite VII with nine pairs of posterior setae. All accessory setae on tergites I–VII sensilliform, 14–15 µm on tergites I–VI and 17 µm on VII. Tergite VIII with setae Mc). Sternite IV–V each with three anterior setae and eight posterior setae (Fig. 8K), VI–VII each with three anterior setae and nine posterior setae, Pc present (Fig. 8L, M). Sternite VIII with 4/2 setae. Hind margin of tergite IX smooth. Hind margin of tergites X–XI with very short fine ciliation. Hind margin of sternites IX–XI smooth. Posterior margin of tergite XII smooth, sternite with delicate serration in central part.

Tergites I and VIII with pores psm only, II–VII with pores psm and al, IX–XI without pores, XII with single medial pore. Sternites I and VI without pores (Fig. 8H, L), II–V each with single medial pore (Fig. 8I, J), VII with single anterior pore asymmetrical located left or right on the line (Fig. 8M), VIII–XI without pores, XII with 1+1 pores al.

Abdominal appendages I, II, III with 2, 1, 1 segments and 4, 2, 2 setae respectively. On appendages II and III, subapical seta 16–18 µm, apical seta 12–15 µm in length. Striate band on abdominal segment VIII well developed, anterior margin regular wave shaped (Fig. 8D). Comb on abdomen VIII rectangular, with 10–12 teeth (Fig. 7K). Female squama genitalis with short basal apodeme and pointed acrostyli (Fig. 7G). Male squama genitalis with 4+4 setae on dorsal side and 2+2 setae on ventral side (Fig. 7L).

Chaetal variability. Chaetal variations were observed in 7 specimens: on tergite II, absence of P4a (No. FE-2011067-2); on tergite IV, asymmetrical absence of A1 of right side (No. FE-2011060-1); on sternite II, absence of Pc and present of P1 on right side (No. FE-2011060-1, Fig. 70); on sternite III, present of Pc (No. FE-2011060-1, Fig. 71); on sternite VI, absence of Pc (Nos. FE-2011067-2, FE-2011088-2, FE-2011089-1); on sternite VIII, asymmetrical absence of P1 of left side (Nos. FE-2011062-3, FE-2011062-5, FE-2011069-1), or both side (No. FE-2011060-1).

Russia (Far East, Magadan Oblast; Khabarovsk Krai).

Imadateiella sharovi (Martynova, 1977) is characterized by the presence of setae Pc on sternite VI and 4/2 setae on sternite VIII.

Imadateiella sharovi (Martynova, 1977) is the first species of Protura described in RFE. We give the redescription of Imadateiella sharovi basing on our vast material since it shows minor differences from the redescription of Shrubovych (2014) (labial palpus, length of sensilla b, e and t2 on fortarsus and pores on sternite I). The male squama genitalis is also described for the first time. The variation on labial palpus is also uncommon – 15 specimens from samples 27 and 24 have labial palpus with reduced terminal tuft of setae (Figs 7D, 8B) while other 5 specimens from samples 26, 30 and 32 have it well developed (Figs 7E, 8C). According to the redescription of Shrubovych (2014), the type specimens have well developed labial palpus. We treat all our populations as belonging to one variable species.