Tenuiphantes zelatus (Zorch, 1937)

Slowik, Jozef, 2018, Tenuiphantes zelatus (Zorsch), T. zibus (Zorsch), and Centromerus mariannae sp. nov. (Araneae: Linyphiidae) in the Pacific Northwest, Insecta Mundi 649, pp. 1-9 : 2-3

Tenuiphantes zelatus (Zorch, 1937)

Fig. 1–4 .

Lepthyphantes zelata Zorsch 1937

Lepthyphantes zelatus Roewer 1942

Tenuiphantes zelatus Saaristo and Tanasevitch 1996

Type. Male with male and 12 female allotypes. Sol Duc Hot Springs, Washington, USA. 12 August 1927. Coll: C. R. Crosby. In AMNH. Examined.

Specimens measured. USA: Alaska: 1 male, Prince of Wales Island, Staney Ck. 1B, 55.872°N 133.06523°W 77 m elv., 12–27 June 2010 coll: J. Stockbridge, C. Bickford, clear cut, pitfall 4, UAM: Ento:227012 ; 1 male, Prince of Wales Island, Luck Pt., 55.98256°N 132.77943°W 129 m elv., 9 July–1 Aug 2010 coll: J. Stockbridge, C. Bickford, 2nd growth, pitfall 2, UAM: Ento:227024 ; 1 male, Prince of Wales Island, Staney Ck. 1B, 55.872°N 133.06523°W 77 m elv., 30 May–12 June 2010 coll: J. Stockbridge, C. Bickford, clear cut, pitfall 4, UAM: Ento:226958 ; 3 Female, Prince of Wales Island, Hatchery Ck. 2, 55.89356°N 132.9437°W 134 m elv., 2–29 June 2010 coll: J. Stockbridge, C. Bickford, 2nd growth, pitfall 1, UAM: Ento:226966 ; 1 male, Prince of Wales Island, Staney Ck., 55.79726°N 133.1363°W 50 m elv., 30 May–10 June 2010 coll: J. Stockbridge, C. Bickford, thin. 2nd growth, pitfall 3, UAM: Ento:226954 ; 1 male, Prince of Wales Island, Hatchery Ck. 4, 55.88602°N 132.8607°W 78 m elv., 14–27 June 2010 coll: J. Stockbridge, C. Bickford, old growth, pitfall 2, UAM: Ento:227007 ; 2 Female, Prince of Wales Island, Hatchery Ck. 2, 55.89356°N 132.9437°W 134 m elv., 2–29 June 2010 coll: J. Stockbridge, C. Bickford, 2nd growth, pitfall 2, UAM: Ento:226967 .

Diagnosis. Male T. zelatus can be distinguished from all other Tenuiphantes species in the Pacific Northwest by a paracymbium with a single basal denticle ( Fig. 1 and 3 , BDP) and a lamella characteristica with a right-angle bend prior to a rounded oblique ventral fork and a single dorsal fork originating near the right-angle bend and curving along the lamella characteristica ( Fig. 2 ). Males of T. zibus lack any denticles on the paracymbium and have an additional dorsal fork originating near the bend in the lamella characteristica and projecting away from the ventral fork ( Fig. 6 ). Males of T. tenuis have two denticles on the paracymbium and a lamella characteristica with both ventral and distal forks curving distally and ending in sharp points ( van Helsdingen et al. 1977, figure 18).

Females can be distinguished by an inversely-heart shaped scape and a posterior plate with wide, laterally directed lateral lobes ( Fig. 4 ). Both T. zibus and T. tenuis females have a longer narrow anterior section of the scape which flares out posteriorly ( Fig. 7 ), creating a pronounced inverted “T” shape in T. tenuis ( van Helsdingen et al. 1977, figure 16). They also have a posterior plate with narrow lateral lobes curving along the lateral edge of the scape. Additionally, specimens of T. zelatus tend to be smaller and darker then T. zibus or T. tenuis .

Description. Male (n = 5). Total length = 1.49–1.59 mm; carapace length = 0.77–0.81 mm; carapace width = 0.63–0.65 mm; carapace L:W ratio 0.82. TmI = 0.23, TmIV absent. Chaetotaxy: F I, 0-1-0-0; F II-IV, 0-0-0-0; Pt I-IV, 1-0-0-0; TiI, 2-1-1-0; TiII, 1-1-1-0; TiIII-IV, 2-0-0-0, MtI-IV, 1-0-0-0. Carapace uniformly dusky. ALE, PME, PLE similarly sized, AME about 3/4 size of other eyes, 1/2 eye width apart. Lateral eyes adjacent, PME separated from lateral eyes by 1/4 eye width, PME 1/2 eye width apart. Clypeus two ALE width. Sternum dusky to dark grey. Abdomen light grey with 2–5 dark chevrons. Dorso-lateral area lined with white. Sides dark. Ventro-lateral area lined with white. Venter uniformly dark. Legs yellow, without bands. Three cheliceral promarginal teeth and one retromarginal denticle. Paracymbium base with several stout hairs, and a single denticle located basally under the curve of the parabymbium thumb. It may be necessary to view the paracymbium dorsally to see the denticle ( Fig. 3 , BDP). The distal ridge of the paracymbium has a circular to oval indentation along the proximal edge, distal section an elongated semi-spatulate shape ( Fig. 1 ) occasionally twisting. Embolus narrow at the point of attachment to the suprategulm with a row of denticles along the base of the ridge, expanding to a denticle-covered bisected spatulate shape with a thumb. Embolus proper spear-shaped. Lamella characteristica directed distally then abruptly turning laterally and widening before narrowing to a tip along the retrolateral side ( Fig. 2 ).

Female (n = 5). Total length = 1.70–1.80 mm; carapace length = 0.77–0.81 mm; carapace width = 0.64–0.66 mm; carapace L×W ratio 0.82. TmI = 0.24, TmIV absent. Chaetotaxy: F I, 0-1-0-0; F II-IV, 0-0-0-0; Pt I-IV, 1-0-0-0; TiI, 2-1-1-0; TiII, 1-1-1-0; TiIII-IV, 2-0-0-0, MtI-IV, 1-0-0-0. Coloration same as male, although generally lighter in color and chevrons on abdomen less visible. Scape inversely-cordate shaped, narrowing and curving under itself before terminating in a narrow projection which extends posteriorly ( Fig. 4 ). Posterior plate wider than scape with a shallow indentation along the ventral edge. Lateral lobes of the posterior plate directed laterally.

Variation. There is some variation in how abrupt the lamella characteristica curve is and the darkness of the apical section which may lead to confusion with T. tenuis . There is little variation in the shape of the scape, which may be confused with that of T. zebra , found in eastern North America. However, the species can be separated by the smoothly curved inversely-cordate shaped scape, and larger atria (compare Fig. 4 to Figure 284 in Kaston (1948) or Figure 1653 in Paquin and Dupérré (2003)). All specimens measured came from coastal Alaska and do appear to be smaller than specimens collected elsewhere, Zorch (1937) states a total length of the males as 1.8–1.9 mm and 2 mm for the females.

DNA barcoding. One UAM specimen (UAM:Ento:149203) was DNA barcoded by Sikes et al. (2017) and falls into BIN BOLD:AAP4445 with 268 other specimens, which is 9.65% distant from its nearest neighbor.

Distribution. The species can be found throughout forested regions of the Pacific Northwest from Oregon to Alaska and eastward to the front range of the Rockies. It does not appear to have a forest habitat preference and is collected in old growth forests, second growth forests as well as clear cuts from sea level to tree line. Mature specimens have been collected from the middle of May to the middle of July, with the majority of adults being collected the first part of June.

Figures

Figures 1–7. Tenuiphantes spp. 1–4) Tenuiphantes zelatus (Zorch, 1937). 1) Lateral view of palp. 2) Ventral view of palp. 3) Mesal view paracymbium. 4) Ventral view of epigynum. 5–7) Tenuiphantes zibus (Zorch, 1937). 5) Lateral view of palp. 6) Ventral view of palp. 7) Ventral view of epigynum. p = paracymbium, lc = lamella characteristica, e = embolus, BDP = basal denticle of paracymbium, s = scape, pp = posterior plate.