Folsomia aquatica Wang & Wu, 2012, sp. nov.

Folsomia aquatica sp. nov.

(Figs 1–12)

Type material. Holotype, female. Honghe Farm, Sanjiang Plain, Heilongjiang Province, China, N 47° 35ʹ, E 133 °31ʹ; 55 m alt., wetlands, 26.v.2011, coll. Haitao Wu. Paratypes, 4 males and 15 females, from the same locality, the same data as holotype. All material deposited in Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences.

Description. Body length up to 1.3mm. White, pigment and ommatidia absent in alcohol.

PAO long and narrow, almost as long as the width of Ant. I and 1.8–2.4 times longer than inner edge of unguis III, with a weak constriction and small inner "denticles" (Fig. 1). Maxillary palp bifurcate, outer maxillary lobe with 4 sublobal hairs.

Labral formula 4/5,5,4. Ventral side of head with 4 postlabial chaetae. Labrum with 4 basomedian and 3 proximal chaetae. labrium with 5 usual papillae (A-E)and full set of guard chaetae. Ant. I with 3 small basal microsensilla (2 dorsal and 1 ventral), and 2 ventral lateral sensilla (Fig. 2). Ant. II with 3 basal microsensilla and 1 lateral distal sensillum. Ant. III with 1 basal microsensillum and 5 distal sensilla (including 1 lateral); sensilla on Ant IV differentiated, 6-7 of which moderaly thickened (Fig. 2).

Sensillar formula for Th. II–Abd.V: 4,3/2,2,2,3,5(s), 1,1/1,0,0 (ms) (Figs 3, 4). Medial sensilla on all tergites situated in front of p-row, fine and curved. Macrochaetae 1,1/3,3,3,4 in number, acuminate and smooth. Medial macrochaetae on Abd. V 4-5 times longer than mucro. Abd. VI without foil-chaetae (Fig. 5). Ventral chaetae on thorax absent. Unguis without inner and lateral teeth. Tibiotarsi of Leg I and II with 25–27 chaetae arranged in 4 rings, respectively (Figs 6, 7). Tibiotarsi of Leg III with 30 chaetae (Fig. 8). Retinaculum with 4+4 teeth and one chaeta on corpus (Fig. 9).

VT wih 4+4 latero-distal and usually 7 (6–10) posterior chaetae (Fig. 10). Anterior furcal subcoxa with 7–10, posterior subcoxa with 4–5 chaetae. Anterior side of manubrium with 1+1 chaetae apically (Fig. 11). Manubrium on posterior side with 3+3 latero-basal, 4+4 central, 2+2 distal, and 1+1 apical chaetae. Lateral side of manubrium with 1+1 chaetae (Fig. 12). Dens with 8 anterior chaetae (Fig. 11) and 3 posterior chaetae (2 basal and 1 medial) (Fig. 12), posterior side crenulated. Mucro with two teeth. Ratio manubrium: dens: mucro = 4.5–6.4: 4.0–5.9: 1.

Remarks. According to systematics of the genus proposed by Potapov (2001), F. aquatica sp. nov. belongs to quadrioculata -group after the following characters: thoracic segments with corner sensillum, medial sensilla on body tergites well in front of p-row of chaetae, medial sensillum on Abd. I–III placed between Mac1 and Mac2 and bifurcate maxillary palp. Absence of ommatidia is common character for F. albens, F. b a i c a l i c a, F. taimyrica, F. villosa and F. vtorovi. The new species may be distinguished from F. atropolaris and F. villosa by 1+1 chaeta on anterior side of manubrium, the latter ones have 11–14 and 12 chaetae, respectively. It differs from F. albens by VT with 4+4 latero-distal and 7 posterior chaetae, the latter with 3+3 latero-distal and 6 posterior chaetae. F. aquatica is very similar to F. taimyrica and F. v t o ro v i distinguished only by microsensillar formula (1,1/1,0,0 in F. aquatica, 1,1/1,1,1 in F. taimyrica and 1,0/1,0,0 in F. v t oro v i). It is also very similar to F. bidentata differing by body length (1.1-1.3 mm in F. aquatica 0.8mm in F. bidentata), PAO length (in former almost as long as width of Ant. I, in latter 1.6 times longer than width of Ant. I) and by the number of posterior chaetae on manunbrium (in former 20 chaetae constantly, in latter with 21 chaetae).

Distribution. Heilongjiang province, China.

Ecology. Wetlands (Deyeuxia angustifolia).

Derivatio nominis. Named after the type of the habitat.