Gasteracantha geminata ( Fabricius, 1798 )

Sankaran, Pradeep M., Jobi, Malamel J. & Sebastian, Pothalil A., 2015, Redescription of the orb-weaving spider Gasteracantha geminata (Fabricius, 1798) (Araneae, Araneidae), Zootaxa 3915 (1), pp. 147-150 : 147-149

Gasteracantha geminata ( Fabricius, 1798)

Aranea geminata Fabricius, 1798: 292 (Description of ♀ (Ramanathapuram, 9o22'14.12''N, 78o50' 0 0.44''E; 10.67 m ))

Gasteracantha geminata C. L. Koch, 1837: 16 , fig. 260 (Description and illustration of ♀).

Plectana geminata Walckenaer, 1841: 158 .

Gasteracantha connata Butler, 1873: 168 (Description of ♀)

Gasteracantha rimata O. P.- Cambridge, 1879: 282, pl. 26, fig. 3 (Description and illustration of ♀)

Gasteracantha geminata Simon, 1895: 836 , figs. 883-887 (Description of ♂ and illustrations of ♂ & ♀). Pocock, 1900: 233, fig. 79 (Description and illustration of ♀). Dahl, 1914: 267, fig. 11 (Illustration of ♀). Tikader, 1982: 53, figs. 107-110 (Description and illustration of ♀). Kim et al., 2013: 175, figs. 1-8 (Description and illustration of ♀).

Material examined. India, Kerala, Alappuzha, Pathiramanal Island (9o37'07.11''N, 76o23'04.95''E), 0 m, Pradeep M.S.

leg. 0 5 February 2014, by hand, 1 ♂, 3 ♀ ( ADSH 096626A). Kerala, Alappuzha, Pathiramanal Island (9o37'07.11''N, 76o23'04.95''E), 0 m, Pradeep M.S. leg. 22 November 2014, by hand, 2 subadult ♂, ( ADSH 096626B).

Diagnosis. G. geminata is most similar to G. k u hl i C. L. Koch, 1837 ( Song et al. 1999, figs. 168G-H, M, S-T). Males of G. geminata can be easily distinguished from those of G. kuhli by the disto-median process of conductor ( Figs. 1 C, 2C) (absent in G. kuhli ), reniform paramedian apophysis ( Figs. 1 C, 2C) (circular in G. kuhli ), median apophysis with distoretrolateral serration ( Figs. 1 C–D, 2C–D) (median apophysis with prolateral serration in G. k u hl i) and large, dorsally inconspicuous posterior opisthosomal spines ( Figs. 1 A, 2A) (posterior opisthosomal spines in G. k u hl i are short and dorsally conspicuous). Females can be distinguished by the M-shaped posterior border line of the epigynum ( Fig. 2 E) (posterior border line in G. kuhli is not M-shaped), posteriorly directed fertilization ducts ( Fig. 2 F) (fertilization ducts in G. kuhli are anteriorly directed) and the long, closely placed paired lateral opisthosomal spines ( Figs. 1 B, 2B) (lateral opisthosomal spines in G. k u hl i are short and widely placed).

Description. Male (from Pathiramanal Island, Figs. 1 A, 2A): Prosoma black; cephalic region provided with a midanterior projection accomodating AMEs; thoracic region provided with numerous tiny tubercles. Clypeus, chelicerae, maxillae, labium, sternum black. Opisthosoma creamy white with black patches; dorsum provided with 20 sigillae arranged as in Fig. 2 A; unlike female, lateral spines on the opisthosoma absent, posterior ones present, but difficult to distinguish in dorsal view ( Fig. 2 A); marginal and ventral opisthosoma provided with numerous tiny, pointed tubercles ( Figs. 1 A, 2A); venter with circular corrugations. Legs yellowish-brown with broad black patches. Body length 3.25. Prosoma length 1.29, width (at the middle) 0.85. Opisthosoma length 1.96, width (at the middle) 1.77. Eyes diameter: AME 0.07. ALE 0.07. PME 0.06. PLE 0.07. Eye interdistance: AME–AME 0.07. AME–ALE 0.19. AME–PME 0.07. PME–PME 0.05. PME–PLE 0.24. Clypeus height at AMEs 0.11, at ALEs 0.11. Measurements of palp and legs: Palp 1.27 [0.29, 0.17, 0.15, 0.66], I 2.87 [0.91, 0.45, 0.58, 0.53, 0.40], II 2.57 [0.84, 0.41, 0.47, 0.46, 0.39], III 1.74 [0.56, 0.27, 0.30, 0.30, 0.31], IV 2.6 [0.89, 0.35, 0.51, 0.49, 0.36]. Leg formula: 1423. Pedipalp ( Figs. 1 C–D, 2C–D): Palpal segments yellowish-brown; cymbium brown. Tibia with a disto-prolateral finger-like extension directed at 10o’clock position ( Figs. 1 C, 2C); RTA with broad base and narrow tip, base of RTA directed at 4o’clock, but its tip at 3o’clock ( Fig. 2 D). Cymbium with a baso-retrolateral extension ( Figs. 1 D, 2D). Embolus with slightly broad base and narrow, blunt tip, directed at 3o’clock position ( Figs. 1 C, 2C). Conductor with a disto-median, filiform process, with distinct ridges ( Figs. 1 C, 2C). Paramedian apophysis nearly reniform, with less sclerotized basal part, lying in close contact with the basal part of embolus ( Figs. 1 C, 2C). Median apophysis serrated ( Figs. 1 C–D, 2C–D).

Female (Pathiramanal Island, Figs. 1 B, 2B): Prosoma brown (dark-black in live specimen). Sternum with a large, median dirty-white patch. Opisthosoma hexagonal, white, provided posteriorly and laterally with paired, thick spines; lateral pairs closely packed, while posterior pair widely separated ( Figs. 1 B, 2B); dorsum provided with three transverse black bands and four rows of large sigillae; venter black with irregularly scattered white patches, transverse corrugations and a large conical tubercle between epigynum and anal tubercle. Legs yellowish-brown with black patches. Body length 7.55 (excluding the posterior spines). Prosoma length 2.65, width (at the middle) 3.19. Opisthosoma length 4.90, width (at the middle) 10.65 (excluding the lateral spines). Eyes diameter: AME 0.05 ALE 0.06. PME 0.05. PLE 0.06. Eye interdistance: AME–AME 0.08. AME–ALE 1.24. AME–PME 0.21. PME–PME 0.10. PME–PLE 1.25. Clypeus height at AMEs 0.22, at ALEs 0.24. Measurements of palp and legs: Palp 3.95 [1.22, 0.62, 0.83, 1.28], I 8.62 [2.70, 1.37, 1.77, 1.78, 1.00], II 8.15 [2.72, 1.29, 1.53, 1.65, 0.96], III 6.21 [2.03, 0.94, 1.15, 1.17, 0.92], IV 9.85 [3.25, 1.28, 2.07, 2.12, 1.13]. Leg formula: 4123. Epigynum ( Figs. 1 E–F, 2E–F): Posterior borderline folded slightly in front, with a median depression to form M-shape ( Fig. 2 E). Scapus short, squarish, as long as the lateral lobes ( Fig. 2 E). Spermathecal head globular with short, wide copulatory duct ( Figs. 1 F, 2F).

Variation. Female body length (n = 3) 7.55–8.02.

Natural history. Both males and females of G. geminata construct orb-webs, preferably in open places among bushes at a height of 0.5 m to 2 m above from the ground level. The web is a highly geometrical orb-web oriented obliquely to the ground level. The adult male spider (described here) was collected from the web of one of the females. Distribution. Known only from India and Sri Lanka (World Spider Catalog 2014).

Figures

FIGURE 1. Gasteracantha geminata (Fabricius, 1798). A, Male, retrolateral. B, Female, dorsal. C, Left male palp, prolateral. D, same, retrolateral. E, Epigynum, ventral. F, same, dorsal. Scale bars: A, 2 mm; B, 1 mm; C – F, 0.5 mm.

FIGURE 2. Gasteracantha geminata (Fabricius, 1798). A, Male habitus, dorsal. B, Female habitus, dorsal. C, Left male palp, prolateral. D, same, retrolateral. E, Epigynum, ventral; F, same, dorsal. Abbreviations: C, conductor; CD, copulatory duct; dC, distomedian process of conductor; E, embolus; FD, fertilization duct; LL, lateral lobe of epigynum; MA, median apophysis; PB, posterior border line of epigynum; PMA, paramedian apophysis; pTA, prolateral tibial apophysis; rCy, retrolateral cymbial extension; RTA, retrolateral tibial apophysis; S, scapus; SH, spermathecal head; T, tegulum. Scale bars: A, 0.61 mm; B, 1.32 mm; C – D, 0.18 mm; E – F, 0.07 mm.