Myrmarachne opaca (Karsch, 1880)

Yamasaki, Takeshi & Ahmad, Abdul Hamid, 2013, Taxonomic study of the genus Myrmarachne of Borneo (Araneae: Salticidae), Zootaxa 3710 (6), pp. 501-556 : 546-547

Myrmarachne opaca (Karsch, 1880)

( Figs 36 A–G)

Synemosyna opaca Karsch, 1880: 395 .

Myrmarachne opaca: Banks, 1930: 211 , Fig. 12 ; Roewer, 1954: 948.

Non-type material examined. BORNEO: 1 male, Lambir Hills National Park, Sarawak, 1–7 XI 2009, T. Yamasaki leg.; 1 male, Inobong, Crocker Range Park, Sabah, 16 XI 2010, T. Yamasaki leg.; 2 males, Maliau Basin, Sabah, 7–10 XI 2011, T. Yamasaki leg.

Diagnosis. In males, thoracic part slightly longer than cephalic part; chelicera apically swollen and basally narrow; fang weakly sinuous without tooth-like apophysis; dorsal scutum on abdomen reddish brown.

Measurements (male). Carapace length 3.05–3.30, width 1.70–1.74. Abdomen length 2.90–3.20. Chelicera length 2.70–3.05. Sternum length 1.85–2.00. Width of eye row I 1.50; II 1.30; III 1.50–1.54. ALE–PLE 1.14–1.18; ALE–PME 0.52–0.54. Eye size: AME 0.46–0.48, ALE 0.24–0.25, PME 0.08–0.13, PLE 0.26.

Male ( Figs 36 A–G). Cephalic part almost flat dorsally, and its posterodorsal corner produced roundly above PLE. Constriction between cephalic and thoracic parts very narrow and deep. Thoracic part convex dorsally, slightly longer than cephalic part; in dorsal view lateral margins of thoracic part convex above coxa III. Chelicera apically swollen and basally narrow, with six prolateral and 15 retrolateral teeth; prolateral teeth confined to anterior half of chelicera. Fang weakly sinuous without tooth-like apophysis. Sternum slender, slightly overlapped by coxae I and III, and strongly by coxa II. Abdomen oval with broad dorsal scutum covering entire dorsum; scutum incised on each lateral outline anteriorly.

Palp ( Figs 36 E–G). Tegulum round with v-shaped seminal reservoir in anterior part. Embolus forming two round coils; embolus coils occupying less than half of venter of cymbium. RTA weakly curved. Flange of RTA not well developed.

Leg spination. Tibia I pv 5, rv 5–6; metatarsus I pv 2, rv 2; tibia II pv 3, rv 3; metatarsus II pv 2, rv 2.

Coloration and pilosity. Carapace dark brown, covered with fine hairs sparsely. Chelicera dark brown, sparsely covered with white hairs dorsally. Maxilla, labium and sternum brown. Coxae tinged with blackish brown. Abdomen covered with very short black hairs; dorsal scutum reddish brown; area except for scutum pale reddish brown.

Distribution. Samar Island (Karsch 1880), Panay Island, Luzon (Banks 1930) and Borneo.

Remarks. The females are unknown. Myrmarachne opaca resembles M. biseratensis in external appearance, and moreover the dentition on the chelicera is similar between them. However, they are easily distinguished by the shape of the fang: the fang is weakly curved in M. opaca , but the basal half strongly arched in M. biseratensis .

Although we did not examine the type material of Synemosyna opaca , Dr. G. B. Edwards showed us pictures of type material, which agreed with the specimens in our collection (personal communication, 2013).

Biology. Myrmarachne opaca is arboreal, and makes retreats on the upper side of leaves. The species often occurs on trees in artificial environments near forests.

Figures

FIGURE 36. M. opaca, male. A, body, dorsal view; B, chelicera and carapace, lateral view; C, chelicera and fang, ventral view; D, maxillae, labium, sternum and coxae; E, palp, ventral view; F, palp, lateral view; G, palpal tibia, dorsal view. (Scales. A – D: 1 mm; E – G: 0.25 mm)

FIGURE 12. M. brevichelicera sp. nov., female. A, body, dorsal view; B, chelicera and carapace, lateral view; C, maxillae, labium, sternum and coxae; D and F, internal structure of epigyne, ventral view; E, internal structure of epigyne, dorsal view. (Scales. A – C: 1 mm; D – E: 0.25 mm; F: 0.10 mm)