Gasteracantha diardi (Lucas, 1835)

Macharoenboon, Kongkit, Siriwut, Warut & Jeratthitikul, Ekgachai, 2021, A review of the taxonomy of spiny-backed orb-weaving spiders of the subfamily Gasteracanthinae (Araneae, Araneidae) in Thailand, ZooKeys 1032, pp. 17-62 : 17

Gasteracantha diardi (Lucas, 1835) Figures 6 , 11D-F

Epeira diardi Lucas, 1835: 70, pl.149, fig. 4. Type locality: Indonesia, Java.

Epeira diardi Full list of synonyms and usage of the name available in World Spider Catalog (2020).

Material.

Thailand • 3 ♀; Chumphon Province, Sawi District, Wisai Tai ; 10°22.38'N, 99°03.61'E; MUMNH-ARA-GAS021 • 3 ♀; Nakhon Ratchasima Province, Pak Chong District, Phaya Yen ; 14°36.97'N, 101°15.90'E; MUMNH-ARA-GAS022 • 1 ♀; Nakhon Si Thammarat Province, Chang Klang District ; 08°19.27'N, 99°35.39'E; MUMNH-ARA-GAS104 • 4 ♀; Nakhon Si Thammarat Province, Phra Phrom District ; 08°22.59'N, 099°52.72'E; MUMNH-ARA-GAS105 • 1 ♀; Chiang Mai Province, Mae Chaem District ; 18°28.81'N, 98°22.96'E; MUMNH-ARA-GAS129 • 4 ♀; Nakhon Ratchasima Province, Pak Chong District, Phaya Yen ; 14°36.97'N, 101°15.90'E; MUMNH-ARA-GAS132 . Cambodia • 3 ♀; Kampot Province; 10°34.92'N, 104°07.21'E; MUMNH-ARA-GAS127 .

Diagnosis.

Sternum dark brown with small median yellow spot. Abdomen much wider than long. Dorsal side of abdomen dark brown. Edge of abdomen with few serrated spikes. Spines dark brown to orange. Anterior spines smallest, slightly directed obliquely. Median spines very large, covered with hairs, and arched backward. Posterior spines conical, pointed backward. Ventral side of abdomen dark brown with scattered yellow spots and small black granules. Ten anterior edge sigilla in total: four sigilla in the middle smaller, forming a straight line, three sigilla on each side larger, trapezoid. Four median sigilla arranged in a trapezoid, with two small sigilla situated on both lateral sides. Posterior edge with ten sigilla in total: six sigilla in the middle forming a straight line, the pair in the middle closely placed; two sigilla on each side larger, trapezoid. Outer posterior edge with five sigilla near posterior spines. Epigynum subtriangular with two lateral dark patches (Fig. 11D ). Scape trapezoid, pointed posteriorly (Fig. 11F ). Spermathecae round (Fig. 11D ), ventrally partially overlapped by wing-shaped sclerotized structure (Fig. 11E ). Copulatory ducts encapsulated by sclerotized structure (Fig. 11D ). Fertilization ducts emerging posteriorly from spermathecae (Fig. 11D ).

Variation.

Four morphotypes were found in this study: (1) the dark brown morph is the most common in Thailand. The dorsal abdomen is plain dark brown (Fig. 6A, B ). This form is concordant with the description by Lucas (1835). (2) A dark red with stripes morph bears three thin yellow stripes near the anterior margin, between median spines, and in front of posterior sigilla (Fig. 6C ). (3) A narrow horizontally banded morph bears three white and three black horizontal lines on dorsal abdomen (Fig. 6D ). The first and the third white bands are very narrow. (4) A broad horizontally banded morph possesses three white and two black horizontal lines on dorsal abdomen (Fig. 6E ). The median spines are bright orange. Ventral side of abdomen is decorated by bright yellow spots.

Remarks.

Gasteracantha diardi can be distinguished from other broad-abdomen Gasteracantha by its large and posteriorly arched median spines, and two additional small sigilla beside the median trapezoid-shaped sigilla. The original description of G. diardi describes the plain dark brown morph specimens ( Lucas 1835). In this study, we report three additional color morphs other than the original description. These color morphs are confirmed by molecular phylogenetic analysis in this study (Fig. 4 ).

Distribution and habitat.

India, China, Laos, Thailand, Malaysia, and Indonesia (Java, Borneo, and Sumatra) ( Butler 1873; Pickard-Cambridge 1879; Dahl 1914; World Spider Catalog 2020). Gasteracantha diardi usually constructs a vertical web between trees, at a height of approximately 2 meters above ground in open areas, and sits at the center of the web.

Figures

Figure 4. Ultrametric tree generated by BEAST from 675 bp of COI gene showing clusters of OTUs as suggested by morphological identification, and three molecular species delimitation algorithms, ABGD, bPTP, and GMYC. Nodal support values are labeled as MP Jackknife support / ML bootstrap values / Bayesian posterior probability. Gene tree from MP and ML analyses are available as Suppl. material 1 (Suppl. material 1: Figs S 3, S 4).

Figure 6. Females of Gasteracantha diardi showing dorsal view (left) and ventral view (right) A, B dark brown morph A specimen from Nakhon Si Thammarat (MUMNH-ARA-GAS 104) B specimen from Nakhon Si Thammarat (MUMNH-ARA-GAS 105) C dark red with stripes morph, specimen from Nakhon Ratchasima (MUMNH-ARA-GAS 132) D narrow horizontal band morph, specimen from Chiang Mai (MUMNH-ARA-GAS 129) E broad horizontal band morph, specimen from Cambodia, Kampot (MUMNH-ARA-GAS 127).

Figure 11. Female genitalia of A-C Gasteracantha diadesmia D-F G. diardi G-I G. doriae J-L G. kuhli. Genitalia are shown in dorsal view (A, D, G, J), ventral view from external (B, E, H, K), and posterior view (C, F, I, L).