Folsomia culter Potapov & Chimitova, 2009, sp. nov.

Folsomia culter sp. nov.

Figs 1–11, 13

Type material. Holotype: female. Russia (East Siberia), Buryat Republic, Vitim Highland, Konda Basin, near Telemba, dense larch wood (Larix gmelini) with no vegetation on ground, ca 930 m alt., 12.viii.2007. 8 paratypes from the same location and 9 paratypes from nearby (ca 10 km NW Telemba), near Birkhasan River, larch wood with covering of Betula frutinosa ssp. montana, ca 1000 m alt., 10.ix.2008, leg. A. Chimitova.

Other material. Several specimens from dry larch wood on a south slope and from a more humid wood with sedge near Telemba (Konda Basin), both of 10.ix.2008, and from mixed forest (Larix gmelini and Betula pendula) with Betula frutinosa and Salix bebbiana near Sosnovo-Ozerskoye (Eravna Basin, Buryat Republic), 6.vii.2008, leg. A. Chimitova.

Description. Body size up to 0.8 mm. Body of typical habitus for the genus (Fig. 1), without pigment. Cuticle with thin, hexagonal, primary granulation ("smooth"). Ocelli lacking. PAO narrow and long, not constricted, 1.5–1.7 as long as width of Ant.I and about twice as long as inner unguis length (1.7–2.1) (Fig. 4). Maxillary outer lobe with 4 sublobal hairs, maxillary palp bifurcate. Labral formula as 4/5,5,4. Labium with 5 usual papillae (А–Е), full set of guard setae, 3 proximal and 4 basomedian setae. Ventral side of head with 4+4 setae along linea ventralis. Ant.I with 2 small basal microsensilla (bms), dorsal and ventral, and 2 ventral sensilla (s), Ant.II with 3 bms and 1 latero-distal s, Ant.III with 1 bms and 6 distal s (including 2 lateral), without additional sensilla (Fig. 4). Sensilla on Ant.IV weakly differentiated. Organite stick-like, slightly swollen at the tip.

Sensillary formula as 4,3/2,2,2,3,5 (s), 1,0/1,0,0 (ms). Tergal sensilla as long or longer than common setae and hardly distinguishable. Sensilla of lateral parts of Th.III–Abd.II (Figs 1–3) longer than others. Medial sensilla on all tergites situated well in front of p-row of setae, on Abd.I–III between Mac1 and Mac2. Abd.V with 5 sensilla arranged with 3 dorsal ones (al, accp1, accp2) much longer than sensilla on Abd.IV and 2 lateral middle-sized sensilla clearly thicker than other sensilla on Abd.IV and Abd.V (Figs 3, 9, 13). Macrochaetae smooth and long, 1,1/3,3,3 in number, medial ones on Abd.V 1,6–1,8 times shorter than dens and 4.5–5.1 times longer than mucro (Fig. 1). Seven strong foil setae at the tip of abdomen arranged in two transversal rows as 2+2 anterior (fa1 and fa3) and 1+2 posterior (fp0 and fp2), respectively. Axial chaetotaxy as 9–11,7–8/4,4,4. Th.III with 2+2 (rarely 2+3) ventral setae.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage 0.5–0.55 as long as unguis. Tibiotarsi with few additional setae, 25–26 and 27–28 on Leg I and II, respectively. Tibiotarsi of Leg III with many setae. Tibiotarsal tenent setae pointed. Ventral tube with 4+4 laterodistal and 5 posterior setae, anteriorly without setae. Tenaculum with 4+4 teeth and 1 seta. Anterior furcal subcoxae with 8–11, posterior one with 5 setae. Anterior side of manubrium normally with 12–14 setae arranged as 3+3, 2+2, 1+1, 1+1. One or two setae missing, so formula can be as 3+3, 2+2, 1+1, 1+0; 3+3, 2+2, 1+0, 1+0; 4+3, 1+2, 1+1, 1+1 (Fig.

6). Posterior side of manubrium with 4+4 laterobasal, 2 apical setae (ap), 3+3 setae in distal transversal row (M1, ml1, L1), two pairs of lateral setae (l1, l2), and 4+ 4 in central part (m, M2, L2, pr). In four individuals studied, no variation of posterior setae of manubrium was observed (Fig. 5). Dens with 23–27 anterior setae, most basal setae considerably enlarged (pointed in Figs 6, 8). Posterior side of dens crenulated, with 6 normal setae (4 basal and 2 at the middle) and one minute seta at the base of mucro (Figs 7, 8). Mucro bidentate. Ratio of manubrium:dens:mucro = 4.6–5.4:7.3–8,4:1.

Discussion. The group to which the species belongs to is not clear cut. The mid-tergal position of sensilla and many setae on manubrium with 3+ 3 in distal transversal row indicates the binoculata -group (Fjellberg 2007) or spinosa -group (Potapov 2001). These groups never have foil setae distally on the abdomen and have a sensillary pattern on Abd.V unlike in F. c u l t e r. The two lateral thickened sensilla on Abd.V are shared with sensibilis -group (see below). Foil setae and chaetotaxy of furca indicate an affinity with several species of fimetaria -group but the position of tergal sensilla is different. The “3+3, 1+1,...” chaetotaxy of manubrium, the long, narrow PAO, long sensilla, and their mid-tergal position are shared with F. hubeiensis Ding et al. (China: Hubei) which belongs to the newly erected hubeiensis -group (Ding et al. 2006). Following the original description and using our own study of several type specimens, F. hubeiensis differs in its pattern of sensilla on Abd.III (medial sensillum is situated between M2 and M3) and on the tip of abdomen (no thickened sensilla), fewer setae on posterior side of dens (3 basal setae instead 4), ventral setae on thorax missing, and other significant features. In many characters F. culter sp. nov. is most similar to F. k u r u s h i c a Potapov, Abdurakhmanov & Aitekova (Russia: Caucasus) and F. tianshanica Martynova (Middle Asia: Tien- Shan). These two species also have an uncertain taxonomic position and differ from F. culter in having three prelabral setae (vs. 4), simple (vs. bifurcate) maxillary palp, weak development of foil setae, ventral setae on Th.III missing, and other features.

Distribution and ecology. Known from several forest sites in two basins of East Buryatia.

Derivatio nominis. The species is armed with seven strong foil setae (“ culter ” is a knife in Latin).