Gasteracantha diadesmia Thorell, 1887

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 diadesmia Thorell, 1887 Figures 5 , 11A-C

Gasteracantha diadesmia Thorell, 1887: 225. Type locality: Myanmar, Bhamo.

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

Material.

Thailand • 3 ♀; Nakhon Ratchasima Province, Wang Nam Khiao District ; 14°32.57'N, 101°58.22'E ; MUMNH-ARA-GAS009 • 3 ♀; Nakhon Ratchasima Province, Pak Chong District, Phaya Yen ; 14°36.97'N, 101°15.90'E ; MUMNH-ARA-GAS011 • 2 ♀; Satun Province, Thung Wa District, Khantiphon Cave ; 07°05.08'N, 99°47.92'E ; MUMNH-ARA-GAS012 • 3 ♀; Ratchaburi Province, Suan Phueng District ; 13°33.03'N, 99°17.14'E ; MUMNH-ARA-GAS028; MUMNH-ARA-GAS030 • 1 ♀; Kanchanaburi Province, Sai Yok District ; 14°24.93'N, 98°52.54'E • 5 ♀; Ratchaburi Province, Suan Phueng District, Pachi Stream ; 13°31.18'N, 99°18.88'E ; MUMNH-ARA-GAS031 • 1 ♀; Chiang Mai Province, Mueang District ; 18°47.00'N, 98°57.13'E ; MUMNH-ARA-GAS034 • 3 ♀; Krabi Province, Mueang District, Krabi Noi ; 08°07.54'N, 98°55.40'E ; MUMNH-ARA-GAS043 • 1 ♀; Bangkok Province, Ratchathewi District, Santiphap Park ; 13°45.68'N, 100°32.42'E ; MUMNH-ARA-GAS045 • 4 ♀; Mae Hong Son Province, Mueang District, Pang Mu ; 19°18.12'N, 97°57.58'E ; MUMNH-ARA-GAS047 • 1 ♀ juvenile; Surat Thani Province, Khiri Rat Nikhom District, Wang Badarn Cave ; 08°54.52'N, 98°57.08'E ; MUMNH-ARA-GAS067 • 2 ♀; Chanthaburi Province, Soi Dao District ; 13°06.67'N, 102°12.30'E ; MUMNH-ARA-GAS076 • 2 ♀; Chanthaburi Province, Mueang District, Khlong Narai ; 12°35.45'N, 102°09.48'E ; MUMNH-ARA-GAS077 • 4 ♀; Kanchanaburi Province, Si Sawat District, Na Suan, Ong-ju Canal ; 14°48.45'N, 99°05.53'E ; MUMNH-ARA-GAS082 • 1 ♀; Phetchabun Province, Lom Sak District ; 16°43.74'N, 101°20.22'E ; MUMNH-ARA-GAS086 • 2 ♀; Chaiyaphum Province, Phakdi Chumphon District, Ban Chiang, Wua Daeng Cave ; 16°04.55'N, 101°26.46'E ; MUMNH-ARA-GAS096 • 1 ♀; Loei Province, Nong Hin District ; 17°02.41'N, 101°44.18'E ; MUMNH-ARA-GAS099 • 2 ♀; Chiang Mai Province, Mae Rim District ; 18°55.10'N, 98°54.51'E ; MUMNH-ARA-GAS102 • 2 ♀; Kanchanaburi Province, Mueang District, Li Chia Cave ; 15°04.50'N, 98°33.96'E ; MUMNH-ARA-GAS107 • 3 ♀; Kanchanaburi Province, Thong Pha Phum District, Huai Kayeng ; 14°37.85'N, 98°34.32'E ; MUMNH-ARA-GAS108 • 5 ♀; Loei Province, Phu Ruea District ; 17°31.55'N, 101°15.33'E ; MUMNH-ARA-GAS117 • 3 ♀; Chiang Mai Province, Fang District ; 19°57.46'N, 99°12.17'E ; MUMNH-ARA-GAS122.

Diagnosis.

Sternum dark brown with median yellow spot. Abdomen much wider than long. Dorsal side of abdomen with three yellow abdominal horizontal bands: first band on anterior edge near base of anterior spines, second band running between median spines, and third band behind middle sigilla reaching posterior edge. Edge of abdomen with serrated spikes, obvious on spines. Spines dark brown to orange. Anterior spines smallest, obliquely directed. Median spines longest, thick, plate-like, horizontally pointed. Posterior spines conical, pointed backward. Two median yellow spots between the bases of posterior spines. Ventral side of abdomen blackish with scattered yellow spots and small black granules. Ten anterior edge sigilla in total: four sigilla in the middle small, forming a straight line, three sigilla on each side larger, trapezoid. Four median sigilla arranged in trapezoid. Ten posterior edge sigilla in total: six sigilla in the middle, forming a straight line, the pair in the middle close together; two sigilla on each side larger, trapezoid. Five outer posterior edge sigilla, placed near posterior spines. Epigynum subtriangular with two lateral dark patches (Fig. 11A ). Scape large, pointed posteriorly, divided into three curves (Fig. 11A, C ). Spermathecae round (Fig. 11A ), ventrally partially overlapped by wing-shaped sclerotized structure (Fig. 11B ). Copulatory ducts encapsulated by sclerotized structure (Fig. 11A ). Fertilization ducts emerging posteriorly from spermathecae (Fig. 11A ).

Variation.

Dorsal dark horizontal bands, spines, and ventral abdomen either reddish (Fig. 5A, D ) or blackish (Fig. 5B, C ) in some specimens. Median spines in some specimens slightly pointed backwards (Fig. 5C ).

Remarks.

Gasteracantha diadesmia resembles Gasteracantha sturi (Doleschall, 1857), but black horizontal bands of G. diadesmia are wider than in G. sturi ( Doleschall 1857; Kolosváry 1931). Moreover, median spines of G. diadesmia are large, thick, and plate-like, while median spines of G. sturi are very blunt. Gasteracantha diadesmia is distinguished from other Thai species by having broader anterior yellow horizontal band and thick, plate-like, and horizontally pointed median spines. Barrion and Litsinger (1995) reported another form with discontinuous dark horizontal bands from the Philippines. However, this morphotype might belong to another species because the shape of spines and color pattern are different.

Distribution and habitat.

India, Myanmar, China, Thailand, Vietnam, Philippines, and Andaman and Nicobar Islands ( Yin et al. 1997; World Spider Catalog 2020). Gasteracantha diadesmia are commonly found in mixed deciduous forest and dipterocarp forest. The spiders usually construct a vertical web between shrubs in open areas, and sit at the center of the web.

Figures

Figure 5. Females of Gasteracantha diadesmia showing dorsal view (left) and ventral view (right) A specimen from Mae Hong Son (MUMNH-ARA-GAS 047) B specimen from Nakhon Ratchasima (MUMNH-ARA-GAS 011) C specimen from Loei (MUMNH-ARA-GAS 117) D specimen from Chanthaburi (MUMNH-ARA-GAS 076).

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).