Tomocerus tropicus sp. nov.

Figs 1A, 2, 3

Type material. Holotype: female on slide, Mt. Wuzhishan National Nature Reserve, Shuiman Township, Wuzhishan, Hainan Province, China, 109°41'15"E, 18°54'11"N, alt. 901 m, 29.xii.2015, litters and humus on rocks, leg. Daoyuan Yu and Chunyan Qin (15HN5) . Paratypes: 2 females, 1 male and 1 subadult on slides, 11 adults and juveniles in alcohol, same data as holotype. All types in NJAU .

Description. Body length 3.3–3.9 mm. General background colouration of body white to light yellow. Ant. I and Ant. II distally with purple pigment, Ant. III and Ant. IV purple. Eye patch black. Diffuse purple pigment around mouthparts. Tibiotarsi purple and other segments occasionally with light purple pigment (Fig. 1A).

Antenna 0.8–0.9× length of body. Length ratio of Ant I:II:III:IV = 1.0:1.3–1.5:8.8–10.0:0.7–0.9. Cephalic dorsal macrochaetotaxy: anterior area: 2 (A2), 4 (A3, A5); interocular area: 2 (M2), 7 (S0, S2, S5, S 5i); postocular area: 2+2 (Pa5, Pa6); posterior area: 2+2 (Pa2, Pp3). Posterior margin of head with 30–40 chaetae on each side (Fig. 2A).

Pattern of body chaetotaxy as in Fig. 2B. Th. II with macrochaetae a3, a4, a4a and a5a behind anterior marginal macrochaetae cluster; a2, a5, m3 and m 4 in central area.

Trochantero-femoral organ with 1, 1 slender chaetae subequal in length (Fig. 2C). Tibiotarsi I, II, III ventrally with 6–7, 6–7, 6 strong chaetae, 3–4, 4, 6 of them blunt (Fig. 2D). Tenent hair 0.8–1.0× length of inner edge of unguis; accessory chaetae slightly longer than pretarsal chaetae; guard chaetae subequal to tenent hair in length. Unguis slender, with baso-internal ridges about 1/4–1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with basal tooth and 4–6 more distal teeth, sub-basal tooth stronger. Unguiculus lanceolate, about 0.6–0.8× length of unguis, its inner edge with one tooth (Fig. 2E).

Ventral tube scaled on both faces. Anterior face with 16–20 chaetae on each side, posterior face with 50–65 chaetae, each lateral flap unscaled, with 50–115 chaetae. Anterior face of tenaculum with 8–18 chaetae and without scales (Fig. 2F). Ratio of manubrium:dens:mucro = 2.9–3.4:4.0–4.4:1.0. Manubrium ventrally scaled without chaetae; laterally with large round scales and 10–11 chaetae, proximal 1–2 chaetae slender and almost smooth, distal chaetae strong and slightly serrated; each dorsal chaetal strip with 125–180 chaetae of different sizes, an irregular row of scales from base to 1/3–1/2 length of manubrium along inner edge, and 10–15 pseudopores on lateral side; 2 pairs of blunt prominent chaetae at centre and near distal end of manubrium, respectively, proximal prominent chaeta longer (Fig. 3A); distal corner chaeta as about size of small mesochaetae in chaetal strip (Fig. 3B). Dens basally with blunt prominent dorsal chaeta. Dental spine formula as 4–5/3–5, 2, sizes of spines gradually increase on basal subsegment (Fig. 3C); denticles on spines unevenly distributed, small spines with basal large denticles and a few small denticles, moderate and large spines dorsally mainly with basal large denticles, ventrally with basal moderate and distal small denticles (Fig. 3D). Mucro with 6–9 intermediate teeth (Fig. 3E).

Etymology. Latin word tropicus: tropical.

Habitat. Mixed forest, in leaf litters and thin layer of humus on rocks.

Remarks. Tomocerus tropicus sp. nov. is characterised by the presence of 4 central macrochaetae a2, a5, m3 and m4 on Th. II, 2+2, 1 blunt prominent chaetae on the furca, dorsal scales on the manubrium, and uneven distribution of different-size denticles on large dental spines. The species resembles Tomocerus pseudocreatus Yu, 2018 in cephalic chaetotaxy, claw complex and furca prominent chaetae, but the latter has mesothoracic central macrochaetae m1 and m2 but not m4, no scales on the dorsal side of manubrium, and almost evenly distributed denticles on large dental spines. Critical characters discriminating T. tropicus sp. nov. from similar species are listed in Table 1.