Folsomia hidakana Uchida & Tamura, 1968

Potapov, Mikhail, Hasegawa, Motohiro, Kuznetsova, Natalia, Babenko, Anatoly & Kuprin, Alexander, 2018, Isotomidae of Japan and the Asiatic part of Russia. I. Folsomia ' inoculata' group, ZooKeys 750, pp. 1-40 : 6-8

Folsomia hidakana Uchida & Tamura, 1968 Figs 10, 13, 21-27, 28, 90

Material.

Japan, Honshu Island, Nobeyama, Nagano, 10.x.2012, coll. M. Hasegawa; Kitaibaraki, 2.xi.2011, coll. M. Hasegawa; Hokkaido Island. Shore of Harutori Lake, Kushiro city, 14.v.2014 and 19.viii.2014, coll. Y. Suma; Shiretoko Peninsula, surroundings of Utoro, litter of mixed forest, 90 m alt., 20.viii.2016, 44.1006°N, 145.0584°E, coll. M. Potapov and N. Kuznetsova; Shiretoko Peninsula, trail to Rausu Mount, ~200 m alt., 29.ix.2013, coll. R. Kitagawa and S. Fujii; ibidem, trail to Rausu Mount, ~1000 m alt, oak litter, coll. M. Potapov and N. Kuznetsova.

North Korea. Hamgyong-namdo Province (= South Hamgyong), valley N from Song-riong, 03.vi.1987, and SW from Tanchon, 30.v.1987, coll. A. Szeptycki.

Far East of Russia, Primorsky Krai, Lazovsky District, nearby Preobrazheniye, litter and rotten wood in deciduous and coniferous forests, 400-700 m alt., 21.ix.2011, coll. M. Potapov, Y. Bu, H. Chen-Wang; Khasansky District, Peschany Peninsula, near Beregovoye, litter under dogrose, 09.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos, Khasansky District, ~15 km S Kraskino, Mramorny Cape, oak wood litter and soil under coastal reed, 28.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Khasansky District, ~15 km W Kraskino, Mayachnoye (Chertova Gorka), forest litter, 28.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Khasansky District, Krabbe Peninsula, Astafyeva Cape, deciduous litter, v.2007, coll. E. Sokolova; Khasansky District, "Kedrovaya Pad", mixed forest, litter, 29.vii.2016, coll. M. Potapov and N. Kuznetsova; ibidem, coniferous and deciduos litter, 29.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; ibidem, 03.x.2009, coll. O. Smirnova, ibidem, v.2015, coll. A. Matalin; Khasansky District, near Barabash, oak wood on slope, litter, 27.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Partizansky District, vicinities of Ekaterinovka, Chondalaz (= Lazovy) Range, oak litter, 26.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Ussuriyski District, Ussuriyski Reserve, decaying wood, 5.x.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Shkotovsky District, Khualaza Mount, 2.x.2004, coll. R. Pomorski; between Vladivostok and Artem, botanical garden, litter of mixed forest, ix.2012 and 04.x.2009, coll. O. Smirnova; Terneysky District, Sikhote-Alimski Reserve, Kabany station, forest litter, 08.viii.2017, coll. N. Kuznetsova, A. Geras’kina, A. Kuprin; Kavalerovski District, road Kavalerovo-Dal’negorsk, 44.3844°N, 135.3639°E, mossy larch forest with Rhododendron , 09.viii.2017, coll. N. Kuznetsova, A. Geras’kina, A. Kuprin; Khabarovsky Krai, Vaninsky District, nearby Datta, coastal larch-wood, 28.ix.2011, coll. M. Potapov; Vaninsky District, five km N Vysokogorny, valley of Mulinka River, larch-forest litter, ~ 600 m alt., 29.ix.2011, coll. M. Potapov.

Description.

Body size from 1.2 to 1.7 mm. Body shape as common for the group, not slender (Fig. 13). Usually with large pigment grains rarely scattered on body, more on fused Abd. IV–VI. Cuticle with fine hexagonal primary granulation ( “smooth”). Ocelli absent. PAO slender, with clear middle constriction, 'inner denticles’ hardly developed, its length 1.2-1.7 as long as width of Ant.I and 1.6-2.0 as long as inner unguis length (Fig. 24). Labium complete, guard setae e7 present, three proximal and four basomedian setae. Ventral side of head with 4+4 postlabial setae. Ant.I with 15-17 common setae, 2-3 (see the discussion below, Figs 23, 24) ventral s-setae (s) and three basal micro s-setae (bms): two dorsal bms (short and long) and one ventral bms. Ant.II with three bms and one latero-distal s, Ant.III with one bms and with 5-6 distal s (one or two lateral s, Fig. 25). Organite varies in shape, often large.

Common setae middle-sized. Setae covering polychaetotic: Abd.IV with 7-9 p-setae between medial accp-s, Abd.V with m1-setae (marked on Fig. 28). Sensillary formula as 43/22235 (s) and 10/100 (ms). S-setae long and thin, as long as common setae. Medial s-setae on Th. II–III situated in front position, nearby Md macrosetae, on Abd. I–III in p-row, between Md and Mdl (Figs 21, 22). Abd.V with five s-setae arranged as four in dorsal position, rather long (as, accp1, accp2, accp3), and one latero-ventral, middle-sized (weakly differentiated ‘4+1’ pattern), accp3 s-setae insignificantly shorter and thicker than accp2 (Fig. 28). Macrosetae smooth, their length vary from long to moderately long, 2,2/3,3,3 in number, medial ones on Abd.V a little shorter than dens (1.0-1.3) and 3.7-6.0 times longer than mucro. Axial chaetotaxy as 9 –12,7–9,/4–5,4– 5,4. Thorax without ventral setae (Fig. 10).

Empodial appendage approximately half as long as unguis. All tibiotarsi with many additional setae: 29-33 on legs I–II, ~38-42 on leg III. Upper and lower subcoxae of legs I–III with 0,1/4 –6,8–11/8–12,8– 11 setae, respectively. Coxae of leg I with four (rarely five) front setae. Ventral tube with 5 –6+5– 6 latero-distal and 6-8 posterior setae, anteriorly without setae. Tenaculum with 4+4 teeth and a seta. Anterior furcal subcoxae with 11-14, posterior one with four setae. Anterior side of manubrium with 4 –6+4– 6 pair setae and usually with two unpaired axial setae (Fig. 26). Posterior side of manubrium with 3+3 latero-basal, two apical setae (ap), 2+2 setae in distal transversal row (M1, L1), one pair of lateral setae, and 4(3)+4(3) in central part (Fig. 27). Dens with 19-23 anterior setae. Posterior side of dens crenulated and with six setae: three basal, two at the middle, and one rudimentary at base of mucro (often hardly visible). Mucro bidentate. Ratio of manubrium: dens: mucro = 3.7-6.2: 4.5-7.0: 1. Males present.

Remarks.

Our specimens fit to the original description of F. hidakana in all significant features. Uchida and Tamura (1968) did not show in figures a subapical rudimentary seta on posterior side of dens and short latero-central setae (l2) on manubrium (probably overlooked). We also found wider variability in most characters that is certainly explained by larger material we have studied. Macrosetae on figures in first description (Figs 28, 35 in Uchida and Tamura 1968) seem to be shorter than in our material. Folsomia hidakana is a peculiar species due to anterior position of medial s-setae on thoracic segments, 5+5 or more latero-distal setae on ventral tube (vs 4+4 that is more common for the group), four setae on posterior furcal subcoxa (fewer than common for the group), 3+3 latero-basal and 1+1 latero-central setae on posterior side of manubrium (fewer than common for the group). The absence of ventral setae on Th.III is the main differentiated feature of F. hidakana shared only with allopatric F. breviseta , the two species are combined in the formal subgroup ' hidakana ' by us. From ' macrochaetosa ' group F. hidakana differ by more setae on body and more lateral position of accp1-s on Abd.V (see Fig. 28 vs Figs 29, 32). Being often mixed with habitually similar species (often with F. imparis sp. n.), F. hidakana is normally easy to recognize by scattered pigment grains on body.

Specimens collected in Japan, both in Honshu and Hokkaido, differ from specimens from Russia by three (vs two) s-setae on Ant.I. In Japanese populations the individuals with two s rarely occur so we keep both variants within diagnosis of F. hidakana .

Distribution and ecology.

Species was described from Hokkaido (Hidaka-Mombetsu) and subsequently listed in catalogues of Japanese Collembola ( Yosii 1977; Furuno et al. 2000; Niijima and Hasegawa 2011). Known from Hokkaido ( Suma 1997, 2008, Hishi et al. 2012), eastern Honshu (Ibaraki) ( Hasegawa et al. 2009), Aomori Pref. ( Yamauchi and Suma 1999, 2009). In Far East of Russia the species was previously recorded near Ussuriysk ( Kutyreva 1988) and in Shikotan Island (as ' F. sp.aff. hidakana ' in Potapov and Marusik 2000).

As a whole, distributional range of the species appears to cover southern area of the Russian Far East, North Korea, and northern half of Japan (Fig. 90). It inhabits forest litter and decaying wood in low mountains, rare in higher altitudes.