Thaiderces jian Li & Li 2017, sp. nov.

Thaiderces jian Li & Li, sp. nov. (Figs 11–12, 15)

Material examined. Holotype male, Thailand, Yala Province, Than To District, evergreen forest in front of Krasaeng Cave entrance (6º10.868’N, 101º11.605’E; elev. 155 m), 10 October 2015, leg. Q. Zhao, G. Zhou & Z. Chen. Paratype. 1 female, same data as holotype (IZCAS).

Etymology. The species name is a noun in apposition derived from the Chinese pinyin "jǐan" ("simple") and refers to the simple structure of the male palp.

Diagnosis. The males of the two species of Thaiderces Li & Li, gen. nov. are very similar but can be distinguished as follows. The embolus of this species is relatively slender basally and the needle-like tip is smoothly curved (Figs 11 A–D) (versus relatively thick basally and with a slightly sinuous tip in T. vulgaris). The female of this species is easily distinguished by the relative length of the pairs of spermathecae: the medial spermathecae are elongate, the lateral spermathecae are greatly reduced (Fig. 12A).

Description. Male (holotype). Total length 1.41; carapace 0.52 long, 0.51 wide; abdomen 0.75 long, 0.44 wide. Carapace round, brown, with two yellow longitudinal bands (Fig. 12C). Fovea shallow, brown. Anterior margin of thoracic region distinctly elevated. Chelicerae yellow with brown spots. Cheliceral promargin with dentoid lamina and no teeth, retromargin with two small teeth, posterior surface of fang with 15 small denticles. Clypeus slanting, pale brown. Labium slanting, brown. Sternum mostly brown with some small yellow areas. Abdomen elongate, light brown, with some yellow patterns dorsally and ventrally. Legs pale brown; measurements: I 5.58 (1.48, 0.20, 1.60, 1.50, 0.80), II 4.54 (1.25, 0.20, 1.25, 1.19, 0.65), III 3.60 (1.00, 0.20, 0.99, 0.94, 0.47), IV 5.31 (1.41, 0.21, 1.53, 1.41, 0.75). Palp (Figs 11 A–D): cymbium simple, unmodified; bulb pale yellow, oval; conductor lacking; embolus arising subapically from bulb, with relatively slender base and smoothly curved, needle-like tip.

Female. Similar to male in coloration and general features but slightly larger (Figs 12 D–E). Measurements: total length 1.60; carapace 0.61 long, 0.54 wide; abdomen 1.05 long, 0.71 wide. Leg measurements: I missing, II - (1.03, 0.22, 1.17, 1.64, -), III 3.02 (0.80, 0.20, 0.79, 0.82, 0.41), IV missing. Vulva with elongate medial spermathecae and very short lateral spermathecae (Fig. 12A).

Distribution. Known only from the type locality (Fig. 15).