Willowsia babykinae

Ecology. Accordingly to the most congeners (bark of the trees).

Description. Body length (excluding antennae) 2.24 mm (n = 1). Ground colour white or very pale, with pigment on the frontal head, antennae, lateral Th II – Abd III and Abd IV, all Th III and AbdV, dorsal Abd III, partially Abd IV, mid posterior AbdV (Fig. 2 E). Scales on dorsal head and dorsal body, 1 + 1 on anterior VT, and on anterior manubrium. Head. Eight eyes, GH slightly smaller than EF (Fig. 7 A). Antennae length 1.29 mm, 2.68 times the length of the head (n = 1); Ant IV with bilobed apical vesicle and a long pin chaeta present; subapical organite very small; sensory organ of Ant III with the special sensilla long-ovoidal, and three guard additional sensilla; relative length of Ant I / II / III / IV = 1 / 1.50 / 1.75 / 2.20 (n = 1); antennae without scales. Prelabral chaetae ciliated. Labral papillae triangular, with a long projection. Lateral process of labial papilla E not or just reaching its apex. Maxillary palp bifurcate, with three sublobal chaetae. Body. Length ratio of Abd IV / III = 4.0 (n = 1). Scale sculpture type B (short rib type, narrow scales, following Zhang et al. 2011) as in Fig. 7 E. Trochanteral organ triangular, with approximately 25 chaetae. Tibiotarsus not sub-segmented, without smooth chaetae, except for smooth terminal chaeta on leg III. Claw with four inner teeth: paired at 50 % and first unpaired at 75 % from the basis, second unpaired sub apical; unpaired dorsal tooth not totally basal, but far of the level of lateral ones (Fig. 7 F). Empodium lanceolate, with serrated external lamella (pe) in leg III. Tenent hair clavate, longer than the claw. Length of manubrium and dens 0.50 and 0.60 mm, respectively (n = 1). Manubrial plate with four chaetae and two pseudopores. Mucro with teeth similar in size, mucronal spine reaching the tip of the subapical tooth; area not crenulated of dens three times the length of mucro. Macrochaetotaxy (Figs 7 A – D). Simplified Mc formula: 3 - 1 - 0 - 3 - 2 / 1 - 4 / 1 - 3 / 0 - 2 - 1 / 0 - 2 - 1 - 2 - 2. Head: H 1 area with Mc An 2, An 3 a 1, and An 3; H 2 area with one Mc (A 5); H 4 area with three Mc (S 1, S 3, and S 4 i); H 4 ’ area with three Mc (S 5, S 5 i and S 4); H 5 area with Ps 2 and Ps 5 Mc. Mesothorax: area T 1 with one Mc (m 1); T 2 with four Mc (a 5, m 4, m 4 i, and m 5). Abdomen: Abd II area A 1 with one Mc (a 2), area A 2 with three Mc (m 3, m 3 ep, and m 3 e); Abd III without Mc on A 3, two on A 4 (a 2 and a 3) and one on A 5 (m 3); Abd IV without Mc on A 6 area, two on A 7 (A 3 and B 3), one on A 8 (B 4), two on A 9 (A 5 and B 5), and two on A 10 (A 6 and B 6); sensillar formula from Th II to Abd V normal as in the rest of Entomobryinae: 2,2 / 1,2,2,7 - n, 3, microsensillar formula from Th II to Abd III: 1,0 / 1,0,1.

Figs 2 E, 7 A – F

Diagnosis. The unequivocal identification of the species can only be done using the abbreviated formula of head (H 1 – 5 areas), Th II (T 1 – 2 areas), Abd II (A 1 – 2 areas), Abd III (A 3 – 5 areas), and Abd IV (A 6 – 10 areas) Mc, as: 3 - 1 - 0 - 3 - 2 / 1 - 4 / 1 - 3 / 0 - 2 - 1 / 0 - 2 - 1 - 2 - 2.

Remarks. The macrochaetotaxy of Abd II – III is usually very stable within Willowsia, allowing species to be easily differentiated (Jordana & Baquero 2005). None of the known species of Willowsia with dorsal macrochaetotaxy formula described shares the formula for Abd II – III with this new species, and only for two species from the Palaearctic region this formula is unknown (W. brahma Imms, 1912 incerta sedis; W. yamashitai Uchida, 1969). The species that share with W. babykinae sp. n. the number and position of the dorsal Mc of Abd III are: W. fascia Pan & Zhang, 2016 (Hubei, Province, China); W. nigromaculata (Lubbock, 1873) Shoebotham, 1917 (Holarctic); W. nivalis Yosii, 1971 (= W. brahmides Yosii, 1966) (Himalaya); W. potapovi Zhang, Chen & Deharveng, 2011 (Caucasus, Azerbaijan); W. pseudosocia Stach, 1965 (Zhang 2015) (Vietnam); W. qui Zhang, Chen & Deharveng, 2011 (Zhejiang Prov., China); W. samarkandica Martynova, 1972 (Uzbekistan); W. similis Pan & Zhang, 2016 (Hunan Prov., China); W. yiningensis Zhang, Chen & Deharveng, 2011 (Xinjiang Prov., China); and W. zhaotongensis Chai & Ma, 2017 (Yunnan Province, China). Only three species share the number of Mc on Th II area T 1: the new species, W. pseudobuski Pan & Zhang, 2016 and W. similis, but the rest of the dorsal macrochaetae formula allows its differentiation. The differences in dorsal macrochaetotaxy (reduced formula of Jordana & Baquero 2005) for all these species are shown in Table 2.

Etymology. The specific epithet refers to Marina Babykina, the researcher of Khingansky Reserve. Her friendly assistance helped us to collect the material this paper is based on.

Type material. Holotype: female on a slide, RUSSIA, Amurskaya Region, Arkhara, under the bark of dead willow (coordinates 49.44424, 130.08451, 145 m a. s. l.), 17. viii. 2014, hand collection, cod. AO 2014 - 1 R- 02. Paratypes (same data as Holotype): one male on the same slide of the holotype (AO 2014 - 1 R- 03), and six specimens in ethyl alcohol (AO 2014 - 1 R- 04 to 09). Kuznetsova, N. and Potapov, M. leg.