Folsomia fumosa Potapov & Gulgenova, 2013, sp. nov.

Folsomia fumosa sp. nov.

Figs 9–15

Type material. Holotype: female. Russia (East Siberia), Irkutsk Area, W Khamar-Daban Range, valley of Slyudyanka River, ca. 10 km SW of Slyudyanka, ca. 1000 alt., litter of poplar wood near the river with Bergenia and Equisetum.), 28.viii.2008, leg. M. Potapov & V. Kadnikov. 4 paratypes from the same locality. 10 paratypes from nearly the same locality, 1300 to 1800 m alt., in taiga belt, in coniferous litter and grass turf. Holotype and 5 paratypes in MSPU; 5 paratypes in BSU.

Other material. Vicinities of Ulan-Ude, ca. 20 km of highway Ulan-Ude–Gremyachinsk, pass, mixed taiga forest, southern slope, 24.ix.2012., leg. N. Nefed'yeva.Shore of Baikal Lake, estuary of Selenga River, Posol'sky Sor Bay, near Baikal'sky Priboy station, weed debris near the water, 23.viii.2011. leg. A. Gulgenova and L. Vanyavina.NW Buryatia, Barguzinsky Range, ca. 10 km W Barguzin, upper flow of Gremyachaya Brook, subalpine belt (Pinus pumila), ca. 1400 m alt., under Bergenia, and ca. 900 m alt., eutrophic mosses near the brook, 20.viii.2008. leg. A. Gulgenova and M. Potapov.

Description. Body size from 0.5 to 0.7 mm. With scattered black pigment grains, general pigmentation varies from almost white (rarely) to spotty fumose (Fig. 11). Body of common shape for the genus. Cuticle with bands of coarse granulation. Ocelli absent. PAO slender, weakly constricted, a little longer than width of Ant I (1.0–1.2) and 1.6–1.9 as long as inner unguis length (Fig. 10). Maxillary outer lobe with 4 sublobal hairs, maxillary palp bifurcate. Labral formula as 4/5,5,4. Labium with 5 papillae (А–Е), e7 present, 3 proximal and 4 basomedian chaetae. Ventral side of a head with 4+4 chaetae. Ant.I with 2 ventral sensilla (s) and 3 small basal microsensilla (bms), 2 dorsal and 1 ventral, Ant.II with 3 bms and a latero-distal s, Ant.III without bms and with 5 distal s (including one lateral), without additional sensilla. Sensilla on Ant.4 weakly differentiated. Organite stick-like, swollen at the tip.

Sensillary formula as common for the genus, 4,3/2,2,2,3,5 (s) and 1,0/1,0,0 (ms). Tergal sensilla a little shorter than common chaetae and rather well distinguishable. Medial sensilla on Th.II–Abd.III situated in mid-tergal position, on Abd.I–III between Mac1 and Mac2 (Fig. 12). Abd.V with 5 sensilla arranged with 3 dorsal ones (al, accp1, accp2), long and slender, 1 lateral middle-sized slightly thickened, and a short sensillum in ventral position (Fig. 14). Macrochaetae smooth and short, 1,1/3,3,3 in number, medial ones on Abd.V about as long as dens (0.9– 1.1) and 2.6–3.3 times longer than mucro. Foil chaetae at the tip of abdomen absent. Axial chaetotaxy as 8–9,7–8/ 4,4,4. Thorax without ventral chaetae.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage about half as long as unguis. Tibiotarsi with 1–3 additional chaetae on Leg I and II (21–24 chaetae), and with up to 6 additional chaetae on Leg III. Tibiotarsal tenent chaetae pointed. VT with 3+3 laterodistal and 5–6 posterior chaetae, anteriorly without chaetae. Tenaculum with 4+4 teeth and a chaeta. Anterior furcal subcoxae with 3–5, posterior one with 3 chaetae. Anterior side of manubrium with a pair of chaetae (Fig. 9). Posterior side of manubrium as in F. palaearctica, with 3+3 laterobasal, 2 apical chaetae (ap), 2+2 chaetae in distal transversal row (M1, L1), one pair of lateral chaetae, and 2+ 2 in central part. Dens with 8 anterior chaetae arranged as 1,1,1,2,3 (Fig. 9). Posterior side of dens crenulated at the middle and with 3 normal chaetae (2 basal and 1 at the middle), without subapical dorsal chaeta. Mucro bidentate. Ratio of manubrium:dens:mucro = 3.6–4.7: 2.5–3.2: 1.

Discussion. The species belongs to ' quadrioculata ' group and mostly resembles F. palaearctica: they share small body size, few chaetae on VT and posterior side of manubrium, bms on Ant.III absent, 1,0/1,0,0 microsensilla. The general appearance of the two mentioned species is also similar. F. f u m o s a sp. nov. differs in the absence of ocelli (present in F. palaearctica), 'p-position' of corner sensilla on Th.II (Fig. 13) (vs. in front of p-row of chaeta), and 8 (vs. 7) anterior chaetae on dens. Both species show similar colouration of the body but in mixed populations F. palaearctica readily differs by distinct dark ocelli. Among blind forms F. f u m o s a sp. nov. resembles the Carpathians F. albens Kaprus’ & Potapov, 1999. The latter species is much paler, has a longer PAO, ms on Abd.I absent, and basal ms on Ant.III present.

Distribution and ecology. F. f u m o s a sp. nov. is probably a local species since it was recorded only in mountain ranges along southern and eastern shores of the Baikal Lake (Fig. 15). It is rather common in Khamar- Daban Range where it is an eurytopic species and it often occurs together with the closely related and somewhat habitually similar species F. quadrioculata, F. manolachei and F. palaearctica. F. f u m o s a sp. nov. is more rare in southern part of Barguzinsky Range and absent both in eastern and western areas (Tunkinskiye Gol'tsy) (Fig. 1: loc. 7, 9, 11, 12). Survives in rather dry conditions (bark of trees, sands).

Etymology. The name is given after the distinctive softly “fumoso” (Latin) coloration.