Plebs opacus Joseph & Framenau 2012, SP. NOV.

PLEBS OPACUS SP. NOV. PACIFIC GRASS ORB- WEAVER (FIGS 23–25)

Araneus neocaledonicus Berland, 1938: 172, figs 126– 128; Bonnet, 1955: 548. (misidentification).

Types: Holotype. ♂ from Sanma Province (Vanuatu), Tataril, Espiritu Santu, (15°21 ′ S, 166°58 ′ E, 1220 m a.s.l., x–xi.1933, Baker (NHM 1934.4.5.12). Paratypes. Three ♀, 14 females, 11 juveniles, same data (NHM 1934.4.5.13–26).

Other material examined: One male and one female from one record (Appendix S1).

Diagnosis: Based on female scape morphology (curved at base) and overall morphology of the male pedipalp, P. opacus is most similar to P. rosemaryae. However, there are subtle differences between the two species in respect to the major pedipalp sclerites of males. The tip of the embolus is heavily twisted in P. opacus, whereas the embolus tip has less curvature in P. rosemaryae (compare Figs 24A and 30A). The conductor of P. opacus is a translucent sclerite in contrast to the opaque conductor of P. rosemaryae. In addition, the apical tips of the median apophysis are comparatively larger in P. opacus. Overall, P. opacus is smaller than P. rosemaryae.

Description

Male: Based on holotype. Carapace orange-brown (Fig. 23A); glabrous with the exception of sparse white setae mainly in cephalic area and in a wide band along lateral margins; one light brown bristle behind PE; fovea Y-shaped, longer than wide. Chelicerae yellow-brown, a band of dark pigmentation running along the dorsal surface reaching up to the mid-region; a few short brown setae mainly in the apical half. Sternum orange-brown, interspersed with streaks of pigmentation; a sparse cover of brown bristles. Abdomen dorsally glabrous, but with a sparse cover of white setae; covered with off-white pigmentation, interspersed with a greenish-brown folium (Fig. 23A); venter with greenish-brown pigmentation (Fig. 23B); weakly covered with white setae. Spinnerets light brown. Legs orange-brown with black annulations, weakly spined, more so on the patella and metatarsus. Coxae of leg IV with three stout setae ventrally. Leg formula 1 > 2 > 4 > 3. Pedipalps (Fig. 24A–C): apex of the median apophysis curved towards cymbium and has two sclerotized apical tips, tegulum with an apical protrusion; terminal apophysis with a marginally sclerotized tip, base sinuous; embolus comparatively short and with sclerotized tip that is curved at right angles, embolus base bulbous; conductor ovate.

Dimensions: total length (excluding chelicerae) 2.85. Carapace length 1.39, width 1.21, height 0.65. Eyes: AME 0.13, ALE 0.08, PME 0.12, PLE 0.08, AME–AME 0.06, AME–ALE 0.08, PME–PME 0.04, PME–PLE 0.15, PLE–ALE 0.02, MOQ width front 0.31, MOQ width back 0.27, MOQ length 0.31, eye group width 0.61. Sternum length 0.61, width 0.48. Abdomen length 1.64, width 1.21. Pedipalp: femur 0.19, patella + tibia 0.15, tarsus 0.50, total 0.84. Leg I: femur 1.54, patella + tibia 2.00, metatarsus 1.16, tarsus 0.54, total 5.24. Leg II: femur 1.35, patella + tibia 1.58, metatarsus 0.96, tarsus 0.46, total 4.35. Leg III: femur 0.62, patella + tibia 0.77, metatarsus 0.46, tarsus 0.35, total 2.19. Leg IV: femur 1.39, patella + tibia 1.09, metatarsus 0.85, tarsus 0.39, total 3.72.

Variation (range): TL 2.85–2.97; CL 1.39–1.45; CW 1.21–1.27; AL 1.64–1.76; AW 1.21–1.33; N = 3.

Female: Based on paratype NHM 1934.4.5.13 from Tataril, West Santo, Vanuatu. Carapace as male, except for an absence of brown bristle behind PE (Fig. 23C). Chelicerae and sternum as male. Abdomen dorsally glabrous, with a sparse cover of white setae; humeral humps present; covered with off-white pigmentation, interspersed with a greenish-brown folium and red pigmented spots (Fig. 23C); four prominent orange-brown sigillae present; venter with greenish-brown pigmentation (Fig. 23D); weakly covered with brown bristles and white setae. Spinnerets light brown. Legs orangebrown with black annulations, weakly spined. Leg formula 1 > 2 > 4 > 3. Epigyne scape elongated, convoluted at the base (Fig. 24E); spermathecae elongate kidney-shaped (Fig. 24D).

Dimensions: total length (excluding chelicerae) 3.21. Carapace length 1.45, width 1.21, height 0.63. Eyes: AME 0.15, ALE 0.12, PME 0.12, PLE 0.12, AME–AME 0.06, AME–ALE 0.13, PME–PME 0.04, PME–PLE 0.17, PLE–ALE 0.02, MOQ width front 0.33, MOQ width back 0.27, MOQ length 0.33, eye group width 0.81. Sternum length 0.91, width 0.79. Abdomen length 1.82, width 1.21. Palp: femur 0.55, patella + tibia 0.48, tarsus 0.42, total 1.45. Leg I: femur 1.94, patella + tibia 2.12, metatarsus 1.45, tarsus 0.61, total 6.12. Leg II: femur 1.52, patella + tibia 1.82, metatarsus 1.03, tarsus 0.55, total 4.92. Leg III: femur 0.97, patella + tibia 1.03, metatarsus 0.55, tarsus 0.36, total 2.91. Leg IV: femur 1.64, patella + tibia 1.58, metatarsus 1.03, tarsus 0.48, total 4.73.

Variation (range): TL 3.03–3.27; CL 1.45–1.52; CW 1.21–1.33; AL 1.82–2.18; AW 1.21–1.33; N = 4.

Remarks: Berland (1938) misidentified P. opacus as P. neocaledonicus, but our examination of specimens from both Vanuatu and New Caledonia showed these to be different species.

Distribution: Vanuatu (Fig. 25).

Life history and habitat preferences: Unknown.

Etymology: The specific epithet is a Latin adjective in apposition meaning ‘shady, dark, obscure’. It refers to the initially obscure identity of this species, which was misidentified as P. neocaledonicus by Berland (1938).