Bioacoustics of Magnacrus tongmianensis

Diagnosis. Females of Magnacrus tongmianensis can be easily distinguished from M. taynguyenensis gen. nov. sp. nov. , by the following: (1) scopula on met. IV well developed and divided (fig. 2H in Zhu et al. 2002 and fig. 2F in Zhu & Zhang 2008 ) vs. weakly developed, undivided ( Fig. 13A ); (2) stridulatory spines on the prolateral palp coxa with 17 spines in M. tongmianensis ( Fig. 1E ) while 10 spines in M. taynguyenensis ( Fig. 7E ); (3) the notch in the middle of the undivided spermatheca ( Fig. 1D ) in the M. tongmianensis is shallow compared to M. taynguyenensis ( Fig. 7D ). Palpal male of M. tongmianensis with 7 keels (PS, PA, PSA, PI, RB, A, SA) and a distinct VTM ( Fig. 3A–F ) vs. five keels (PS, PA, PI, SA, A) and without VTM ( Fig. 6A–F ) in M. taynguyenensis ; M. tongmianensis with two spines on the ventral tibia I apically ( Fig. 2D ) vs. absent in M. taynguyenensis ( Fig. 5D ); ERF in M. tongmianensis is ca. 33 ( Fig. 3F ) while M. taynguyenensis is above 40 ( Fig. 6F ).

Description of male (TNU-THE-005). Body length: 44.5 (including chelicerae). Color (in life) ( Fig. 4B ): Femora of legs dark brown, rest of front legs light brown, tips of metatarsi and tarsi dark brown. Legs dorsally with distinct elongated beige stripes. Carapace and abdomen brown. Carapace ( Fig. 2A ): length 17.0, width 14.5. Fovea low, Fovea: 1.87 wide, curve length 1.89, slightly recurved. Chelicerae ( Fig. 2F ): length 9.5, width 6.0. strong, reddish setal fringe along promargin. Clypeus: width 0.63, smaller than width of OT. Eyes: OT length 2.19, width 2.56. Anterior row almost straight, posterior row slightly procurved. Diameter (longitudinal) ALE: 0.62; AME: 0.68; PLE: 0.53, PME: 0.58; inter-distances: ALE – AME: 0.17; AME – AME: 0.33; PLE – PME: 0.03; Maxillae ( Fig. 2E ): length (incl. trochanter) 11.0. Prolaterally plano-convex, anterior prolateral lobe wellpronounced. Retrolateral face mostly glabrous. Prolateral face with a stridulating organ consisting of 20 thorn-like black spines pointing forward and increasing in length and size from posterior to anterior and dorsal to ventral, in three rows; of these, 4 small thorn-like spines are located between the actual spine arrangement and the suture. Fine plumose setae above suture intermixed with four longish spiniform setae, dorso-anterior edge with a row of elongated black spiniform setae. Labium: length 2.87, width 1.81, wider posteriorly, anterior and posterior edge procurved. Many small black cuspules (~67). Sternum ( Fig. 2B ): length 8.09, width 6.70. Wider posteriorly than anteriorly, with a thin intermix of short setae and sparse longer setae, more so along edges. No spines on edges, but thicker setae along opposing edges of coxa IV. Sternal sigilla: three pairs (not including labio-sternal sigilla), glabrous, PSS largest, ovoid, length 0.80, 0.84 from sternum edge, 3.04 between PSS and clearly visible. Middle and anterior pair obscured by setae, middle pair smaller than PSS and anterior pair smaller than middle pair. Labiosternal groove: glabrous, slightly narrower medially, groove with low oblong cuticular mound on either side of medial narrowing. Leg setation: all legs covered with short pile setae with scattered longer guard setae. Leg I & IV tibia with pro and retrolateral fringe of short pile setae. Legs: formula I, IV, II, III. LRF~ 101. Leg lengths (fem., pat., tib., met., tar., total): I 16.5, 8.5, 16.0, 13.0, 9.5, 63.5. II 16.0, 6.5, 12.5, 11.5, 8.0, 54.5. III 13.0, 6.0, 9.0, 10.5, 9.0, 47.5. IV 17.0, 6.0, 15.0, 17.0, 8.0, 63.0. Tar. IV uniform without transverse pallid medial suture. Tibia apophysis on leg I ventral with a single prolateral apophysis with numerous spines at its tip ( Fig. 2C–D ). Scopula: met. I–III and tar. I – IV, undivided; met. IV divided. Met. I: 88%; II: 73%; III: 54%; IV: 41%. Coxae: coxae I – IV covered ventrally with fine setae, intermixed with longer darker setae, apically, darker basally. Leg I almost as long as IV, 1.17 times the length of II. IV widest, not as rectangular as III. Prolateral margins of II–IV, retrolateral margins of I–IV and apical ventral margins of I–IV, increasing from anterior to posterior, with longer setae, absent along prolateral margin of I. Ventral measurements for coxa + trochanter: length: I 12; II 11; III 10; IV 11. Fine plumose setae on prolateral face, intermixed with numerous elongated black spiniform setae. Spines: Leg: I Tib. 1 v, a, rl; 1 v, a, pl; Met. 1 v, a, pl; 1 v, a, m; II Tib. 1 v, a, rl; 1 v, a. pl; Met. 1 v, a, rl; 1 v, a, m; 1 v, a, pl; III Tib. 1 v, a, pl; 1 v, a, rl; Met. 1 d, a, pl; 1 d, a, rl; 1 v, a, pl; 1 v, a, m; 1 v, a, rl; IV Tib. 1 v, a, pl; 1 v, a, rl.; Met. 1 v, sm, pl; 1, v, a, pl; 2 v, a, m.; 1 v, a, rl. Claws: all unarmed, no third claw on leg IV. Abdomen: length 18.0, wide: 13.0 Palpal bulb ( Fig. 3A–F ): Embolus with seven keels, PS, PA, PSA, PI, RB, A and SA keel, tegulum ventrally basal with a bulge-like process (VTM), ERF~ 33. Spinnerets: PMS: length 0.98; PLS: length 5.42. Additional description to female (TNU-THE-00002). Body length: 55 (including chelicerae). Color (in life) ( Fig. 4A ): Femora of legs dark brown, rest of front legs light brown, rear legs gray brown, carapace light beige, opisthosoma gray brown. Patella, tibia and metatarsus IV retrolaterally with a dense fringe of longer reddish setae. Femur I have a retroventral fringe of short dense red setae. Carapace ( Fig. 1A ): length 20.5, width 15.5. Fovea: 2.38 wide, 2.45 curved length, procurved. Chelicerae ( Fig. 1F ): length 11.0, width 4.0. Retrolaterally with a large field of plumose setae, baso-dorsally with a smaller field of strong plumose setae, baso-ventrally with 5 long, sword-shaped plumose setae. Clypeus: width 0.8, clearly smaller than width of OT. Eyes: OT length 2.20, width 3.12. Diameter (longitudinal) ALE: 0.81; AME: 0.73; PLE: 0.64, PME: 0.59; inter-distances: ALE – AME: 0.34; ALE – PLE: 0.24; PLE – PME: 0.15; PME – AME: 0.14; AME – AME: 0.41. Maxillae ( Fig. 1E ): length (incl. trochanter) 12.09. Prolaterally plano-convex, anterior prolateral lobe wellpronounced. Retrolateral face mostly glabrous. Prolateral face with 17 short thorn-like black spines pointing forward and increasing in length and size from posterior to anterior, in two rows, fine plumose setae above suture, dorso-anterior edge with a row of 11 elongated black spiniform setae. Labium: length 2.34, width 2.83. 88 cuspules in anterior area of labium. Sternum ( Fig. 1B ): length 10.16, width 7.86. Wider posteriorly than anteriorly, with a thin intermix of short setae and sparse longer setae, more so along edges. No spines on edges, but thicker setae along opposing edges of coxa IV. Sternal sigilla: three pairs (not including labio-sternal sigilla), glabrous, PSS largest, ovoid, length 1.15, 0.77 from sternum edge, 3.53 between PSS and clearly visible. Middle and anterior pair obscured by setae, middle pair smaller than PSS and anterior pair smaller than middle pair. Labiosternal groove: glabrous, slightly narrower medially. Leg setation: all legs covered with short pile setae with scattered longer guard setae. Leg IV patella, tibia and metatarsus with dense retrolateral brush of longer guard setae ( Figs 1C , 4A ). Legs: formula IV, I, II, III. LRF~ 85. Leg lengths (fem., pat., tib., met., tar., total): palp 12.0, 7.0, 7.5, –, 7.5, 34; I 14.0, 8.0, 11.0, 8.0, 7.5, 48.5; II 12.0, 7.0, 8.0, 8.0, 6.5, 41.5; III 12.0, 6.5, 6.0, 7.5, 6.0, 38; IV 16.0, 8.0, 14.0, 13.0, 6.0, 57. Pat., Tib. + Met. of leg III and IV strongly incrassate. Tar. IV uniform without transverse pallid medial suture. Scopula: met. and tar. I–IV, undivided. Met. I: 75%; II: 68%; III: 60%; IV: 45%. Coxae: coxae I – IV covered ventrally with fine setae, intermixed with longer darker setae, apically, darker basally. Leg I almost as long as IV, 1.17 times the length of II. IV widest, not as rectangular as III. Prolateral margins of II–IV, retrolateral margins of I–IV and apical ventral margins of I–IV, increasing from anterior to posterior, with longer setae, absent along prolateral margin of I. Ventral measurements for coxae + trochanter: length: I–13; II–12; III–10; IV–13. Spines: Palp Tib.: 1 v, a, rl; 2 v, a, pl; Leg: I Tib.: 1 v, a, pl; Met.: 1 v, a, m; II Tib.: 1 v, a, rl; Met.: 1 v, a, rl; 1 v, a, m; 1 v, a, pl; III Tib.: 1 v, a, rl; 1 v, a, pl; Met.: 1 d, a, rl; 1 d, a, pl; 1 v, a, rl; 2 v, a, m; IV Tib.: 1 v, a, rl; 4 v. a, pl (other Leg: 2 v, a, pl); Met.: 1 d, a, pl; 1 v, sm, pl; 1 v, m, pl (other Leg: 1 v, sm, pl; 1 v, sa, pl); 6 v, a, rl; 5 v, a, pl. Claws: all unarmed, no third claw on leg IV. Abdomen: length 20, wide: 20. Genitalia ( Fig. 1D ): Spermatheca undivided and consisting of two lobes connected by a dent in the middle. Width 4.11, height at the highest point of the left lobe 0.94, of the right lobe also 0.94, at the lowest point in the middle 0.63. The angle between the two lobes is 133.43°. Spinnerets: PMS: 1.59; PLS: length 7.74. Natural history. Specimens of M. tongmianensis were collected from low elevations (below 600 m elev.). The once existing tropical deciduous lowland forest in the region now consists mainly of agricultural development (corn, tangerines) with rubber plantations and small fragmented secondary forests ( Fig. 14A ). The self-excavated fossorial retreats of M. tongmianensis were found on gently sloped ground amongst shaded vegetation in clay-like soil at the fringes of secondary forest or plantations at an elevation of 500 meters. Retreats of adult females averaged 5 cm in diameter and 40 cm in length and ran somewhat parallel under the ground surface, unbranched, curving upwards and ending in a blind chamber ( Fig. 14C ). M. tongmianensis incorporates surrounding organic debris with silk around the entrance rim of the retreat. What is remarkable here is the arrangement of foliage and leaves around the burrow entrance. These are often arranged in such a way that rainwater flows past the burrow entrance due to the arrangement of the leaves and thus does not enter the burrow. A similar arrangement of leaves at the burrow entrance was observed with Cyriopagopus doriae (Thorell, 1890) in Borneo. There, too, rainwater was prevented from entering the burrows by the roof-like arrangement of leaves at the burrow entrance ( Koh 2024 ). Occupied retreats are usually silken over by day, possibly to prevent predacious ants and wasps from entering ( Fig. 14B ). When extracted from the retreat, M. tongmianensis will become very defensive and readily bite if further provoked ( Fig. 14D ). Nothing is known about the life cycle of M. tongmianensis . Males were found wandering in July and it is suspected this is the breeding season for this species, during the highest rainy season from June through to the end of August in the Central Highlands of Vietnam (Q. D. Hoang & T. D. Nguyen, pers. obs.). Ethnozoology. A local ethnic mix of Kinh and Mnong people call these spiders Nhện lông which means ‘hairy spider’ and treat them with mixed ideas. Some local people reported the venomous bite from this spider will kill a water buffalo, but without evidence, while other people collect, cook and eat these spiders (arachnophagy) with great appeal and as a supplement food source. Taylor (1975) investigated the nutritional values of the tarantula spiders eaten in Cambodia and Laos and found they were 63.4% protein and 9.8% fat by body weight. Further, a few village people reported they kill and soak these spiders in wine to make a traditional medicine for rubbing on their skin to cure aches, sprains and bruising (Q. D. Hoang, pers. obs.).