Sason hirsutum, Schwendinger, 2003

Schwendinger, Peter J., 2003, Two New Species Of The Arboreal Trapdoor Spider Genus Sason (Araneae: Barychelidae) From Southeast Asia, Raffles Bulletin of Zoology 51 (2), pp. 197-207 : 202-205

Sason hirsutum , new species

( Figs. 33-41 )

Material examined. – Holotype – male (MHNG), waterfall ca. 7 km N of Daik (00 08’53.3'’S, 104 36’13.2'’E), 60 m, Pulau [=Island] Lingga, Riau Province, Indonesia, coll. P.J. Schwendinger, 15 Jun.2001.

Other – 1 juvenile (8.2 mm body length; damaged) (MHNG), same data as for the holotype .

Diagnosis. – Similar to S. andamanicum , male distinguished by: cuspules on labium and maxillae quite short and stout ( Figs. 35, 36 ); tibia I with row of longer and thinner retroventral spines; tibial spur less elevated, situated more distally, carrying a megaspine less strongly inclined from axis of leg ( Fig. 39 ); distal margin of tibia I less deeply invaginated ( Fig. 38 ); bulb with basally thinner, not sigmoid embolus ( Figs. 40, 41 ).

Description. – Male (holotype). Coloration uniformly light reddish brown on dorsal side, ventral side lighter. Opisthosoma cream, with dark brown-violet pattern dorsally ( Fig. 33 ) and ventrally ( Fig. 37 ). Ocular area dark; posterior zone in front of eyes grey, anterior zone hyaline with black median patch ( Fig. 34 ). Leg tarsi and distal part of metatarsi ventrally white; distal portion of tibia IV and lateral sides of patella IV slightly darkened. Dorsodistal portion of cymbium white.

Carapace ( Fig. 33 ) hirsute, with dark bristles and fine light hairs on pars cephalica and on coxal elevations of pars thoracica; long bristles along lateral carapace margins. Ocular tubercle low; eye group slightly rhomboidal, arranged in three rows; ALE in front of others; AME largest ( Fig. 34 ). Fovea very deep, recurved.

Chelicerae ( Fig. 33 ) weak, cheliceral groove with six/seven teeth on promargin, long reddish bristles on retromargin and one/two tiny denticles basally between them. Rastellum absent.

Maxillae ( Figs. 35, 36 ) with three strong, short cuspules on prolateral-proximal corner.

Labium ( Figs. 35, 36 ) with 10 fairly short, strong cuspules in transverse row distally, median cuspules slightly more slender (but not recognisably shorter) than lateral ones.

Sternum ( Fig. 36 ) separated from labium by shallow groove; only posterior two pairs of small, oval, submarginal sigilla discernible.

Palpus ( Figs. 40, 41 ) with cymbium carrying scopula dorsodistally and filiform, spatulate and clavate dorsal trichobothria dorsoproximally. Bulbus ovoid; embolus fairly straight and slender, with narrow base.

Legs (left leg IV regenerated) 31=24, densely covered with quite long hairs. Paired tarsal claws without teeth. Thin ventral scopula on all tarsi and on metatarsi I and II. Scopuliform hairs on metatarsi distinctly longer than on tarsi. Filiform trichobothria in two parallel rows dorsally on tibiae and metatarsi; three to six clavate and spatulate trichobothria dorsally in proximal half of tarsi and triangular field (widening distally) of filiform trichobothria in distal half. All femora with longitudinal row of five to six long, curved spines (or stiff bristles) dorsally. Low prolateral coupling spur on tibia I carrying strong, blunt megaspine pointing away from axis of tibia at acute angle. Spur only slightly set back from distal margin of tibia I. Prolateral distal edge of tibia I moderately invaginated, i.e. small unpigmented area extending from distal margin of tibia to prolateral (but not proventral) base of tibial spur ( Fig. 38 ). Four long, pointed, curved spines (the distal one weakest) in longitudinal retroventral row on tibia I ( Figs. 38, 39 ). Same arrangement of spines also present on tibia II, but there prolateral-distal spine thin, tapering, not raised on spur. Spinnerets ( Fig. 37 ): PMS short digitiform; PLS three-segmented, apical segment short, with cluster of distal spigots.

Female. Unknown.

Measurements. – Body length 9.3; carapace 4.3 long, 3.9 wide; maxillae 1.4 long, 0.8 wide; labium 0.3 long, 0.7 wide; sternum 2.4 long, 2.1 wide; opisthosoma 4.4 long, 3.0 wide; PMS 0.3 long, PLS 1.3 long. Eye sizes and interdistances: AME 0.50, ALE 0.25, PME 0.14, PLE 0.17; AME-AME 1.12, ALE-ALE 0.73, PME-PME 0.83; eye group length 0.77, front width 1.18, back width 1.31; MOQ length 0.52, front width 1.04, back width 1.02.

Remark. – Palpal claw tufts are not discernible in the damaged juvenile, which indicates that they may also be absent in females.

Etymology. – Latin adjective “hirsutum” = shaggy, hairy. The species epithet refers to the long dense hair on the legs of the male holotype.

Distribution. – This species is known only from its type locality, an island in the Lingga Archipelago, off the east coast of Sumatra.

Biology. – The spiders were collected from silken nests on trunks of living trees (as described above for S. sundaicum , new species) in tropical evergreen rainforest along a stream, several kilometres from the coast. About 30 nests were found, all on trees close to the stream, none further away than ca. 50 m, but only two nests were occupied.

The male holotype was mature when collected in mid-June; its nest was 2.5 cm long, the front door 1.6 cm and the hind door 1.4 cm wide.

Figures

Figs. 33-41. Sason hirsutum, new species, male holotype. 33, body (without legs and palps), dorsal view; 34, eye group, dorsal view; 35, labium and proximal portion of maxillae, ventral view; 36, maxillae, labium and sternum, ventral view; 37, opisthosoma, ventral view; 38, left tibia I, prolateral view; 39, the same, ventral view; 40, distal part of palpus, ventral view; 41, the same, retrolateral view. Scale lines (33+37; 34; 35; 36; 38-41) = 1.0 mm.