Plebs arleneae, Joseph & Framenau, 2012

Joseph, Mathew M. & Framenau, Volker W., 2012, Systematic review of a new orb-weaving spider genus (Araneae: Araneidae), with special reference to the Australasian-Pacific and South-East Asian fauna, Zoological Journal of the Linnean Society 166 (2), pp. 279-341 : 300-303

PLEBS ARLENEAE SP. NOV.

ARLENE’ s GRASS ORB- WEAVER ( FIGS 10 , 11 , 14 )

Types: Holotype. ♂ from Queensland ( Australia), Black Mountain , 26°25 ′ S, 152°51 ′ E, 1971–72, N.C. Coleman ( QM S88901 ) . Paratypes. Three ♂, data as holotype ( QM S88900 ) ; ♀ from New South Wales ( Australia), Hornsby , Waitara Creek, 33°42 ′ S, 151°06 ′ E, 28.x.2001, G. Milledge & H. Smith, beating shrubs ( AM KS74980 ) .

Other material examined: Forty-nine males, 70 females, and 12 juveniles from 79 records (Appendix S1).

Diagnosis: Plebs arleneae can be easily distinguished from other members of the genus by the shape of the median apophysis, which is distally widened and protrudes significantly beyond the tegulum. It bears three tips in a three-dimensional pattern in contrast to the typical two-tipped median apophysis of all other Australian Plebs (with the exception of P. patricius ) ( Fig. 11A–C ). Unique within Plebs , a group of long, strong setae arises from the tip of the cymbium in P. arleneae (‘cymbial setae’ in Fig. 11A ). Males lack the coxal setae that are found in most other members of the genus (except P. patricius ). The epigynal scape of females of P. arleneae is the shortest in comparison to all other Plebs ; however, it is almost always broken off (as in P. patricius ).

Description

Male: Based on holotype. Carapace light orangebrown; glabrous with the exception of sparse white setae mainly in cephalic area and in a narrow band along lateral margins, three light brown bristles behind PE; fovea shallow, longitudinal ( Fig. 10A ). Chelicerae yellow-brown, a band of dark pigmentation running along the dorsal surface reaching up to the mid-region; a few black setae mainly in the apical half. Sternum orange-brown with dark pigmentation along the entire border, sparsely covered with brown bristles. Abdomen: dorsally with light greenish-brown folium; sparse cover of white setae; brown tubercles along the entire dorsum, each tubercle bearing a light brown bristle ( Fig. 10A ); venter with light greenish-brown pigmentation, the typical U-shaped white pattern very faint and the two white spots lateral to the spinnerets absent ( Fig. 10B ); weakly covered with light brown bristles. Spinnerets light brown. Legs orange-brown, moderately spined. Pedipalps ( Fig. 11A–C ): median apophysis protruding beyond tegulum, apex widened, with three broad apical tips with the middle tip more pointed and sclerotized; tegulum with an apical protrusion; terminal apophysis with an unsclerotized, short tip; embolus with a heavily sclerotized tip; conductor short, ovate; a tuft of long setae arising from the apical tip of cymbium and extending over terminal apophysis.

Dimensions: total length (excluding chelicerae) 2.30. Carapace length 1.09, width 0.91, height 0.58. Eyes: AME 0.12, ALE 0.08, PME 0.10, PLE 0.04, AME–AME 0.04, AME–ALE 0.06, PME–PME 0.02, PME–PLE 0.07, PLE–ALE 0.02, MOQ width front 0.23, MOQ width back 0. 19, MOQ length 0.21, eye group width 0.40. Sternum length 0.85, width 0.61. Abdomen length 1.27, width 0.97. Pedipalp: femur 0.15, patella + tibia 0.23, tarsus 0.92, total 1.30. Leg I: femur 1.16, patella + tibia 1.31, metatarsus 0.69, tarsus 0.39, total 3.55. Leg II: femur 0.85, patella + tibia 1.04, metatarsus 0.58, tarsus 0.35, total 2.82. Leg III: femur 0.50, patella + tibia 0.54, metatarsus 0.31, tarsus 0.27, total 1.62. Leg IV: femur 0.77, patella + tibia 0.73, metatarsus 0.42, tarsus 0.35, total 2.27.

Variation (range): TL 2.12–2.31; CL 0.96–1.16; CW 0.89–0.96; AL 1.21–1.35; AW 1.09–1.16; N = 5.

Female: Based on paratype AM KS74980 from Hornsby, New South Wales. Carapace as male, except for absence of bristles (as in Fig. 10C ). Chelicerae as male. Sternum as male. Abdomen subtriangular; dorsum as male, with a broad area of triangular greenish-brown pigmentation along the entire dorsum (as in Fig. 10C ); venter as male. Spinnerets light brown. Legs orange-brown with dark annulations, weakly spined. Leg formula 1> 2> 4> 3. Epigyne with short, triangular scape ( Fig. 11F ), which is almost always broken off ( Fig. 11E ); spermathecae pear-shaped ( Fig. 11D ).

Dimensions: total length (excluding chelicerae) 4.36. Carapace length 1.94, width 1.52, height 0.58. Eyes: AME 0.13, ALE 0.12, PME 0.13, PLE 0.12, AME–AME 0.04, AME–ALE 0.19, PME–PME 0.04, PME–PLE 0.21, PLE–ALE 0.02, MOQ width front 0.33, MOQ width back 0.33, MOQ length 0.35, eye group width 0.92. Sternum length 0.91, width 0.79. Abdomen length 2.67, width 2.00. Palp: femur 0.67, patella + tibia 0.48, tarsus 0.55, total 1.70. Leg I: femur 1.94, patella + tibia 2.55, metatarsus 1.58, tarsus 0.61, total 6.68. Leg II: femur 1.88, patella + tibia 2.06, metatarsus 1.39, tarsus 0.55, total 5.88. Leg III: femur 1.03, patella + tibia 1.82, metatarsus 0.61, tarsus 0.48, total 3.94. Leg IV: femur 1.94, patella + tibia 2.00, metatarsus 1.27, tarsus 0.61, total 5.82.

Variation (range): TL 3.43–4.36; CL 1.42–1.94; CW 1.16–1.52; AL 2.46–2.77; AW 1.96–2.23; N = 3. Abdominal colour variation ranges from a light brown folium ( Fig. 10C ) to a greenish-brown triangular pattern covering the entire dorsum ( Fig. 10E ). Epigynal scape morphology (when present) varies from conical to triangular ( Fig. 11F ).

Distribution: Eastern Australia (Queensland, New South Wales) ( Fig. 14 ).

Life history and habitat preferences: Mature P. arleneae are generally found between October and May (most between November and February), although a single record from Queensland is from July. The species appears to be reproductively active in summer. Habitat descriptions include closed forest, coastal woodland, rainforest, and vine forests, but spiders have also been found on buildings and shrubs.

Etymology: The specific epithet is a matronym in honour of the senior author’s daughter, Arlene Mathew. We propose the common name ‘Arlene’s grass orb-weaver’ for this species.

Figures

Figure 10. Plebs arleneae sp. nov. A, B, male from Atherton Plateau, Rose Gums Wilderness Retreat, Queensland (ZMUC 12190). A, dorsal view; B, ventral view. C, D, female from Atherton Plateau, Rose Gums Wilderness Retreat, Queensland (ZMUC 12190). C, dorsal view; D, ventral view. E, F, female from Jamieson Park, New South Wales (AM KS81995). E, dorsal view; F, ventral view. Scale bar = 0.6 mm in A, B; 1.0 mm in C-F.

Figure 11. Plebs arleneae sp. nov. A, B, pedipalp of male from Atherton Plateau, Rose Gums Wilderness Retreat, Queensland (ZMUC 12190). A, ventral view; B, dorsal view. C, pedipalp of male from Doubleduke State Forest, New South Wales (AM KS88022), apicoventral view. D, epigyne of female from Jamieson Park, New South Wales (AM KS81995), dorsal view. E, epigyne of female from Atherton Plateau, Rose Gums Wilderness Retreat, Queensland (ZMUC 12190), ventral view. F, epigyne of female from Hornsby, Waitara Creek, New South Wales (AM KS74980), ventral view. Scale bar = 0.2 mm in A-D; 0.3 mm in E, F.

Figure 14. Distribution records of Plebs arleneae sp. nov. (O) and Plebs arletteae sp. nov. (•) in Australia.