Cybaeus adenes, Chamberlin & Ivie, 1932

Bennett, Robb, Copley, Claudia & Copley, Darren, 2019, Cybaeus (Araneae: Cybaeidae): the adenes species group of the Californian clade, Zootaxa 4711 (2), pp. 245-274: 246-247

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Cybaeus adenes


The adenes  species group

Diagnosis. Differentiating species of the Holarctic and Californian clades of Cybaeus  is discussed in Copley et al. (2009). The species of the adenes  group of the Californian clade are diagnosed by the undivided, concave to inverted U–shaped atrium ( Figs 4View FIGURES 4–8, 15View FIGURES 15–17, 21View FIGURES 21–24, 30View FIGURES 28–30, 38View FIGURES 38–43, 47View FIGURES 47–49) and the reduced, sinuous vulval ducts with very short, laterally projecting copulatory ducts and short spermathecal stalks ( Figs 6View FIGURES 4–8, 17View FIGURES 15–17, 23View FIGURES 21–24, 49View FIGURES 47–49, 55View FIGURES 54–55). Other Californian clade species groups have the vulval ducts more complex ( Copley et al. 2009: Figs 12, 95, 101) or reduced but linearly oriented ( Copley et al. 2009: Figs 6View FIGURES 4–8, 65View FIGURES 65–68) and/or longer and more complex copulatory ducts ( Copley et al. 2009: Figs 6, 8View FIGURES 4–8 –12, 72, 75, 78, 84, 95, 101).

Description. Small- to medium-sized spiders, carapace lengths averaging 1.73–2.6 (males) and 1.94–2.8 mm (females). Abdomen usually patterned as in Copley et al. (2009: fig. 3) and Bennett et al. (2016: Figs 1–2View FIGURES 1–3), legs unbanded in most species (femora lightly to strongly banded in C. amicus  , C. auburn  , and C. torosus  ). Two complete pairs of ventral tibia I macrosetae: pattern 2-1p-2-1p-0.

Male: Patellar apophysis (Figs 13, 36, 45, 51) prominent, digitiform, length 2/3 ( C. auburn  , Fig. 19View FIGURES 18–20) to nearly as long as (all other adenes  group species) width of patella. Peg setae variable in number, diagnostic for some species. Retrolateral tibial apophysis carinate, nearly as long as tibia (Figs 14, 27, 37, 46). Inconspicuous retrolateral ridge dorsal to retrolateral tibial apophysis often present ( C. adenes  , C. amicus  , C. grizzlyi  , C. reducens  , C. sanbruno  , C. schusteri  : Figs 3View FIGURES 1–3, 14, 27, 36, 46). Embolus ( Figs 1View FIGURES 1–3, 56, 58–59View FIGURES 56–60, 62–68View FIGURES 61–64View FIGURES 65–68) relatively short, thick. Distal arm of tegular apophysis ( Figs 1View FIGURES 1–3, 58View FIGURES 56–60) short, not enlarged or lengthened. Proximal arm of tegular apophysis ( Figs 1View FIGURES 1–3, 18View FIGURES 18–20, 56–68View FIGURES 56–60View FIGURES 61–64View FIGURES 65–68) prolaterally directed with species specific morphology.

Female: Atrium ( Figs 4View FIGURES 4–8, 15View FIGURES 15–17, 21View FIGURES 21–24, 30View FIGURES 28–30, 41View FIGURES 38–43, 47View FIGURES 47–49, 54View FIGURES 54–55) simple, undivided, medially or anteromedially located on epigynum, of variable form; broad and slightly concave ( Figs 21View FIGURES 21–24, 38, 41View FIGURES 38–43) to narrower and strongly vase- or inverted U-shaped ( Figs 4View FIGURES 4–8, 9View FIGURES 9–11, 15View FIGURES 15–17, 30View FIGURES 28–30, 33View FIGURES 33–34, 47View FIGURES 47–49, 53View FIGURES 50–53). Vulva ( Figs 6View FIGURES 4–8, 22View FIGURES 21–24, 39, 43View FIGURES 38–43, 48View FIGURES 47–49) simple, each half sinuous. Copulatory ducts usually separate at atrium (broadly contiguous across anterior of atrium in C. auburn  , Fig. 24View FIGURES 21–24), relatively short, often very broad at atrium; proceeding laterally to outer margins of vulva then turning medially towards vulval midline. Spermathecal heads simple, small, dorsal lobes; occasionally becoming incorporated into surface of copulatory ducts and less distinctly lobe–like, particularly in older individuals ( Figs 29View FIGURES 28–30, 31–32View FIGURES 31–32). Stalks very short, undifferentiated, with well-developed Bennett’s glands at junction with bases ( Figs 6View FIGURES 4–8, 31–32View FIGURES 31–32). Bases simple, rounded with fertilization ducts exiting posteriorly close to junction with stalks.

Composition and distribution. Nine species: Cybaeus adenes Chamberlin & Ivie  , C. amicus Chamberlin & Ivie  , C. auburn Bennett  spec. nov., C. grizzlyi Schenkel  , C. pearcei Bennett  spec. nov., C. reducens Chamberlin & Ivie  , C. sanbruno Bennett  , C. schusteri Bennett  spec. nov., and C. torosus Bennett  spec. nov. All species have restricted distributions in west central California from Sonoma and Napa Counties south to northern Monterey County and east central California (one species, C. auburn  ) from Placer and El Dorado Counties ( Figs 69–71View FIGURE 69View FIGURE 70View FIGURE 71).