Taksinus bambus Songsangchote, Sippawat, Khaikaew & Chomphuphuang, 2021 from Tak, Thailand.

The characteristics of Taksinus gen. nov. that differ from Ornithoctonus and Cyriopagopus are: a low caput, a clypeus that is less than the width of the median ocular quadrangle (Fig. 6A), and spermathecae with twin seminal receptacles (Fig. 7E, F) (Raven 1985; von Wirth and Striffler 2005; Smith and Jacobi 2015). The new genus differs from Citharognathus by the lack of incrassate tibia and metatarsus IV. Taksinus gen. nov. differs from Lampropelma by the absence of a dense brush of hair on the retrolateral side of the femora of the front limbs (von Wirth and Striffler 2005) and males by lack of apical embolus swelling (Fig. 5A–E; see Gabriel and Sherwood 2019: 143, figs 17, 18). Taksinus gen. nov. can be distinguished from Omothymus by male palpal bulb with a gently curved embolus with rounded embolic apex (Fig. 5A–E) vs palpal bulb steep angle embolus and apex with a sharp point in Omothymus (Fig. 5F–J; see Gabriel and Sherwood 2019: 139, figs 1–5). Taksinus gen. nov. differs from Phormingochilus by the lack of a single megaspine on the inside of the male tibial apophyses (Fig. 4A, B; see Smith and Jacobi 2015: 41, fig. 38; Gabriel and Sherwood 2019: 142, figs 14–16), a short embolus compared to palpal bulb length (1:1) (Fig. 5A–E), and the geographic distribution of Phormingochilus currently restricted to Borneo.

The generic name was named Phraya Tak (governor of Tak province), which is in honor of Taksin the Great, king of the Thonburi Kingdom, in commemoration of his early career.

Carapace longer than wide, low caput. Fovea deep, straight (males) or slightly procurved (females). Clypeus short, less than width of median ocular quadrangle in males and females. Eight eyes arranged on tubercle, anterior eye row slightly procurved and the posterior row straight. Outer cheliceral on lower surface from margin with five slightly curved pad of plumose setae on the retrolateral chelicerae. Maxillae longer than wide with >155 cuspules (male) or 149–183 (females), two horizontal rows of 10–11 stout thorn-like spines on the lower half of prolateral maxillae (below suture) and one horizontal row of six stout thorn-like spines on the upper half of prolateral maxillae (above suture). Spines of varying lengths, with the longest being at the top of the series; combined to form a stridulating organ. Labium wider than long, with 75 cuspules (male) or 125 (females). Sternum longer than wide, with two pairs of ovoid sigillae; Posterior sigilla is significantly remote from the edge, middle sigilla is close to the margin, and anterior sigilla is indistinguishable. Legs: formula 1423 (males); ± Total lengths of legs I and IV = 0.48, 4123 (females) ± Total lengths of legs I and IV = 2.41–3.33, RF = 101 (males) or 90.6–93 (females). Scopulae distinct, thickly set on tarsus; ventral surface not divided. Tibial spur capped with multitude of thin, short black spines, with no single megaspine on the inside of the tibial apophyses. Palpal bulb is ellipsoid and partly concave, embolus short compared to palpal bulb length (1:1), moderately curved, rounded apex, with single retrolateral keel. Spermathecae have twin seminal receptacles, rounded tombstone receptacles, fused in the basal region.

Tak province, Thailand

Thailand • Holotype 1 ♂ (TAK1); Mae Tho, Mueang Tak district, Tak province. Paratype 2 ♀ (TAK 2–3 ♀); the same data as the holotype. Specimens were deposited at ENTOKKU (holotype TAK1 ♂ and paratype TAK2 ♀ ID: ENTOKKU TAK1–2) and THNHM (paratype TAK3 ♀ ID: THNHM-Ar-00005).

Figure 3. 

Taksinus bambus sp. nov. Holotype ♂ TAK1 A chelicerae, retrolateral view B maxilla, prolateral view C palpi, labium, maxilla, and coxae, ventral view. Scale bars: 1 mm.

Same as for the genus.

Figure 4. 

Taksinus bambus sp. nov. Holotype ♂ TAK1. Tibial apophysis A ventral view B apical view C prolateral view D dorsal view. Scale bars: 1 mm.

The species name bambus refers to the species, which was discovered in a bamboo plantation and lives in Asian bamboo stalks.

Male TAK1 holotype (ENTOKKU): color in life: leg black, carapace brownish yellow. Total length (including chelicerae) 26.30 mm; cephalothorax 11.09 mm long, 7.62 mm wide, 4.40 mm high (caput); fovea 2.28 mm wide, straight, deep; cephalothorax brown, with a cover of short, whitish-yellow hairs dorsally, long whitish-yellow hairs on lateral margins; clypeus 0.23 mm; ocular tubercle 1.50 mm long, 2.59 mm wide. The anterior eye row slightly procurved and posterior row straight; eyes whitish, ALE oval and larger than the round AME; Eye sizes: AME, 0.45 mm; ALE, 0.88 mm; PLE, 0.48 mm; PME, 0.31 mm. Inter-eye distances: AME–AME, 0.62 mm; AME–ALE, 0.32 mm; AME–PME, 0.30 mm; ALE–ALE, 1.90 mm; ALE–PME, 0.34 mm; PME–PME, 1.40 mm; PME–PLE, 0.10 mm; PLE–PLE, 2.00 mm; and ALE–PLE, 0.32 mm. Chelicerae dark brown, 7.65 mm long, outer cheliceral face with short scopula edge with rows of orange-red setae, the lower surface of the outer cheliceral has five slightly curved plumose setae pads on the retrolateral chelicerae (Fig. 3A). Maxillae reddish brown, 6.06 mm long, 3.49 mm wide with >155 cuspules, covered with orange-red setae on the prolateral surface; stridulation organ consisting of stout thorn-like spines with 11 in two rows (7.4 mm from below suture) and six in one row (1.9 mm from above suture) on the prolateral maxillae (Fig. 3B). Labium brown, length 1.3 mm, width 2.0 mm, with >75 cuspules damaged and loss encompassing approximately 40% of the proximal edge (Fig. 3C). Sternum dark brown, covered with two hair types: strong dark and soft white; 6.41 mm long, 4.38 mm wide with two pairs of ovoid sigillae present near the lateral margins opposing coxa II and III. Sigilla: anterior pair absent; median pair 0.40 mm long, 0.25 mm wide, close to the sternal margin; posterior pair 0.79 mm long, 0.36 mm wide, 0.66 mm from the sternal margin. Abdomen 10.89 mm long, 7.71 wide, dark gray, black thickly hirsute laterally and ventrally. Legs: Pat, Tib, Met, and Tar dark brown. Length of legs and palpal segments are shown in Table 1, leg formula 1423. Spination: tibia II r 0–0–1 (apical), III r 0–0–2 (apical), metatarsus I v 0–0–1 (apical), II v 0–0–1 (apical), III d 0–0–1 (apical), v 0–0–1 (apical), IV d 0–0–1 (apical), v 0–0–3 (apical).

The male tibia I spur is present and lacks a single megaspine on the inside of the tibial apophyses (Fig. 4A–D). Scopulae on metatarsi and tarsi I through IV, undivided. Tar I–IV with two claws; spinnerets covered with dark longer and thinner hairs; Posterior lateral spinnerets with three segments, basal 2.3 mm, median 1.5 mm, digitiform apical 3.0 mm; lateral median spinnerets with one segment 1.25 mm. Pedipalps reddish brown, covered with longer and thinner hairs; tibia swollen; cymbium with two lobes of light brown shaggy scopulae; bulb and embolus 1.76 mm long, dark reddish brown; palpal bulb ellipsoid and partly concave, 1.60 mm long, 1.63 mm wide; embolus moderately curved, rounded apex, with single retrolateral keel (Fig. 5A–E).

Figures 5. 

Taksinus bambus sp. nov. holotype ♂ TAK1 (A–E) and Omothymus sp. ♂ (F–J). Palpal bulb A prolateral view B retrolateral view C dorsal view D ventral view E apical view F prolateral view G retrolateral view H dorsal view I ventral view J apical view. Scale bars: 1 mm.

Paratype ♀ TAK3: total length (including chelicerae) 30.82 mm; cephalothorax 13.43 mm long, 10.39 mm wide, 2.98 mm high (caput); fovea 1.28 mm wide, slightly procurved, deep; cephalothorax brown, covered with short whitish hairs dorsally, golden yellow to yellowish-brown long hairs on lateral margins (Fig. 6A); clypeus 0.13 high; ocular tubercle 1.70 mm long, 2.92 mm wide. Anterior eyes with long hairs in front of AME and mid-posterior PME area; anterior eye row slightly procurved and posterior row straight. Eye sizes: AME, 0.45 mm; ALE, 0.71 mm; PLE, 0.54 mm; PME, 0.37 mm. Inter-eye distances: AME–AME mm, 0.47; AME–ALE, 0.41 mm; AME–PME, 0.25 mm; ALE–ALE, 1.75 mm; ALE–PME, 0.54 mm; PME–PME, 1.27 mm; PME–PLE, 0.66 mm; PLE–PLE, 1.57 mm; and ALE–PLE, 0.39 mm. Chelicerae dark brown, 6.78 mm long, outer cheliceral face with short scopula margin with rows of orange-red setae, outer cheliceral on the lower surface with five slightly curved pads of plumose setae on the retrolateral chelicerae. Maxillae reddish brown, 3.83 mm long, 2.10 mm wide with >183 cuspules, covered with orange-red setae on the prolateral surface, labium brown, length 1.51 mm, width 2.09 mm, with >125 cuspules covering approximately 40% of the proximal edge (Fig. 6D). Sternum dark brown, covered with two types of hairs: strong dark and soft white; 5.89 mm long, 5.54 mm wide with two pairs of ovoid sigillae present near lateral margins opposite coxa II and III (Fig. 6B). Sigilla: anterior pair absent; median pair 0.35 mm long, 0.27 mm wide, close to the sternal margin; posterior pair 0.75 mm long, 0.32 mm wide, 0.72 mm from the sternal margin. Abdomen 15.58 mm long, 10.95 mm wide, dark gray and black thickly hirsute laterally and ventrally. Legs: Pat, Tib, Met, and Tar dark brown. Length of legs, palpal segments, and the comparative leg measurements are shown in Table 2, leg formula 4123. Spination: tibia palp r 0–0–1 (apical), p 0–0–1 (apical), r 0–0–2 (apical), I p 0–0–1 (apical), II p 0–0–1 (apical), r 0–0–1 (apical), III p 0–0–1 (apical), IV r 0–0–1 (apical), p 0–0–1 (apical), metatarsus I v 0–0–1 (apical), II v 0–0–1 (apical), III d 0–0–1 (apical), v 0–0–1 (apical), p 0–0–1 (apical), r 0–0–2 (apical), IV v 0–0–3 (apical). Scopulae on metatarsi and tarsi I through IV undivided. Tar I–IV with two claws; spinnerets covered with dark brown longer and thinner hairs; posterior lateral spinnerets with three segments, basal 2.03 mm, median 1.40 mm, digitiform apical 2.10 mm; lateral median spinnerets with one segment 1.21 mm. Spermathecae (Fig. 7F): paired and divided with fused in base, base 0.88 mm (left) and 1.00 mm (right) long, 1.10 mm (left) and 1.06 mm (right) wide; sclerotization heaviest apically, gradually decreasing basally.

Figure 6. 

Taksinus bambus sp. nov. Paratype ♀ TAK3 (A, B, D) Paratype ♀ TAK2 (C). A carapace, dorsal view B sternum, labium, maxilla, and coxae, ventral view C maxilla, prolateral view D maxillae and labium with cuspules. Scale bars: 1 mm.

Paratype ♀ TAK2: dark brown, carapace brown. Total length (including chelicerae) 34.80 mm; cephalothorax 14.39 mm long, 11.57 mm wide, 3.16 mm high (caput); fovea 1.20 mm wide, straight, deep; cephalothorax brown, covered with short whitish hairs dorsally, golden yellow to yellowish-brown long hairs on lateral margins; clypeus 0.15 mm high; ocular tubercle 1.83 mm long, 2.70 mm wide. Anterior eyes with long hairs in front of AME and mid-posterior PME area; anterior eye row slightly procurved and posterior row straight. Eyes whitish, ALEs oval in shape, larger than the round AMEs. Eye sizes: AME, 0.44 mm; ALE, 0.69 mm; PLE, 0.59 mm; PME, 0.40 mm. Inter-eye distances: AME–AME, 0.37 mm; AME–ALE, 0.49 mm; AME–PME, 0.30 mm; ALE–ALE, 1.69 mm; ALE–PME, 0.68 mm; PME–PME, 1.20 mm; PME–PLE, 0.17 mm; PLE–PLE, 1.86 mm; and ALE–PLE, 0.50 mm. Chelicerae dark brown, 7.02 mm long, outer cheliceral face with short scopula margin with rows of orange-red setae; outer cheliceral on the lower surface with five slightly curved pad of plumose setae on the retrolateral chelicerae (Fig. 7B, C) with cheliceral needle form strikers (Fig. 7B, D). Maxillae reddish brown, 3.64 mm long, 2.21 mm wide with 149 cuspules, covered with orange-red setae on the prolateral surface, stridulation organ consisting of stout thorn-like spines with 10 in two rows (7.4 mm from below suture) and six in one row (3.0 mm from above suture) on the prolateral maxillae (Fig. 6C). Labium brown, length 2.29 mm, width 1.45 mm, with >7 cuspules damaged and lost. Sternum dark brown, covered with two types of hairs: strong dark and soft white; 6.22 mm long, 5.33 mm wide, with two pairs of ovoid sigillae present near the lateral margins opposite coxa II and III. Sigilla: anterior pair absent; median pair 0.51 mm long, 0.26 mm wide, close to the sternal margin; posterior pair 0.73 mm long, 0.32 mm wide, 0.45 mm from the sternal margin. Abdomen 18.72 mm long, 11.42 mm wide, dark gray and black thickly hirsute laterally and ventrally. Legs: Pat, Tib, Met, and Tar dark brown. Length of legs, palpal segments, and the comparative leg measurements are shown in Table 3, leg formula 4123. Spination: tibia palp r 0–0–1 (apical), p 0–0–1 (apical), r 0–0–2 (apical), I p 0–0–1 (apical), II p 0–0–1 (apical), r 0–0–1 (apical), III p 0–0–1 (apical), IV r 0–0–2 (apical), p 0–0–1 (apical), metatarsus I v 0–0–1 (apical), II v 0–0–1 (apical), III v 0–0–1 (apical), p 0–0–1 (apical), r 0–0–2 (apical), IV v 0–0–3 (apical). Scopulae on metatarsi and tarsi I through IV, undivided. Tar I–IV with two claws; spinnerets covered with dark longer and thinner hairs; posterior lateral spinnerets with three segments; basal 2.10 mm, median 1.36 mm, digitiform apical 2.19 mm; lateral median spinnerets with one segment 1.34 mm. Spermathecae (Fig. 7E): paired and divided with fused in base, base 0.90 mm (left) and 1.07 mm (right) long, 1.09 mm (left) and 1.17 mm (right) wide; sclerotization heaviest apically, gradually decreasing basally.

Figures 7. 

Taksinus bambus sp. nov. paratype ♀ TAK2 (A–E) paratype ♀ TAK3 (F). A chelicerae, prolateral view B chelicerae, retrolateral view C plumose hairs outer chelicerae, retrolateral view D chelicerae strikers, retrolateral view E spermathecae, dorsal view F spermathecae, dorsal view. Scale bars: 1 mm.

Specimens were collected from villages surrounding Tak province at approximately 1,000 m elevation. The biotope consists of a mixed deciduous forest dominated by bamboo that is rarely disturbed by human activity (Fig. 8A). The new arboreal tarantula shows a surprising specialization in that it lives in the stalks of Asian bamboo (Gigantochloa sp.) (Fig. 8B–E). All specimens were collected from bamboo internodes in mature culms, having nest entrances approximately 2–3 cm within a silk-lined tubular burrow at the entrance located in the branch stub or at the middle of the bamboo culms. Some specimens had a secondary entrance without silk at the hole (Fig. 8B). Tarantulas do not bore bamboo stems; instead, they depend on the assistance of other animals. Bamboo is attacked by numerous animals, the most common of which are insects from the orders Coleoptera, Lepidoptera, and Diptera (Varma and Sajeev 2015). Furthermore, we hypothesized that the tarantula might occupy the empty nest of insects, such as the bamboo-nesting carpenter bee Xylocopa, which creates a large hole. All the tarantulas living in the bamboo culms build silken retreat tubes that cover the stem cavity (Fig. 8C–E).

Figures 8. 

Taksinus bambus sp. nov. from Tak province, Thailand A biotope, bamboo forests in mountainous slope areas B tarantula habitat in bamboo culm with entrance hole (below) and secondary entrance (upper) C, D tarantula in bamboo culm E tarantula building silk tube retreats on the cover culm F paratype ♀, TAK3 T. bambus alive.