Cybaeus aspenicolens Chamberlin & Ivie 1932

The aspenicolens species group

Diagnosis. Differentiating the species groups of the Holarctic and Californian clades of Cybaeus is discussed in Copley et al. (2009). The species of the aspenicolens group of the Californian clade are defined by the atrium usually divided and with longitudinal copulatory openings leading into the midline of the vulva (Figs 16, 18, 38) and the greatly reduced and linearly oriented copulatory ducts and spermathecal stalks (Figs 19, 22, 37). Other Californian clade species groups are characterized either by a divided atrium but a more complex vulva with the copulatory ducts and spermathecal stalks not so reduced or linear (septatus group–Copley et al. 2009: figs 12, 95, 101), an undivided atrium and simple but sinuous copulatory ducts and spermathecal stalks (adenes group–Bennett et al. 2019: figs 6, 8, 11, 17, 24, 29, 31, 32, 34, 40, 48, 55), or the atrium divided or not and relatively long and complex copulatory ducts (consocius, devius, and tardatus groups–Copley et al. 2009: figs 8–10, 72, 75, 78, 84).

Two informal subgroups are definable within the aspenicolens group: the aspenicolens subgroup (C. aspenicolens, C. blasbes, and C. coylei spec. nov.) and the fraxineus subgroup (C. fraxineus spec. nov. and C. thermydrinos). Males of the aspenicolens subgroup are characterized by their possession of a large, broad, blunt patellar apophysis with dimorphic peg setae in two groups (Figs 2, 5, 8, 11–13) and the large, C-shaped proximal arm of the tegular apophysis with a retrolaterally directed uncinate tip (Figs 3, 6, 9), Males of the fraxineus subgroup can be distinguished by their narrower and tapered patellar apophysis with monomorphic peg setae in a single group (Figs 25, 29) and the proximal arm of the tegular apophysis smaller with a prolaterally directed bifurcate tip (Figs 26, 30, 32–33). Females of the aspenicolens subgroup are characterized by their conspicuous epigynal concavity or depression and atrial openings without a transverse hood (Figs 14, 16, 18). Females of the fraxineus subgroup have an epigynum with a “normal”, relatively convex surface and atrial openings partially obscured anteriorly by a transverse epigynal ridge or hood (Figs 34–35, 38–39).

Description. Medium- to large-sized spiders, carapace lengths averaging 2.6–3.3 mm (males) and 2.4–3.4 mm (females). Abdomen patterned, femora usually at least lightly banded. Two or three complete pairs of ventral tibia I macrosetae (terminal pair absent, incomplete, or present): pattern 2–1p–2–1p–0 (or 1p, or 2).

Male: Patellar apophysis distally directed, species specific; massive, blunt, broader than long, length about 3/4 patellar width, with dimorphic peg seta separated in two groups retrolaterally and dorsally (Figs 2, 5, 8, 11–13); or slenderer, gradually tapering to blunt point, longer than broad, length about equal to width of patella, with monomorphic peg setae in single group dorsally along posterior margin of distinct concavity (Figs 25, 29). Palpal tibia about as long as wide; retrolateral tibial apophysis carinate, nearly as long as tibia (Figs 1–2, 25). Embolus relatively short, thick (Figs 3, 5, 9, 26, 30). Distal arm of tegular apophysis short, not enlarged or lengthened; proximal arm species specific, retrolaterally or prolaterally directed (Figs 3–4, 6–7, 9–10, 26–28, 30–31).

Female: Epigynum usually ridged anteriorly; atrium inconspicuous with medial paired, longitudinal openings (Figs 14, 18, 38). Vulva (Figs 19, 22, 39) simple with reduced, nearly linear copulatory ducts and spermathecal heads and stalks. Copulatory ducts very short, exiting atria towards midline of vulva, often contiguous along midline. Heads of spermathecae on small dorsal lobes near midline of vulva; often not differentiated from rest of vulva except for presence of primary pores. Stalks very short, not differentiated. Bennett’s glands near junction of stalks with rounded, relatively large spermathecal bases. Fertilization ducts exit bases near junction with stalks.

Composition and distribution. Cybaeus aspenicolens Chamberlin & Ivie, C. blasbes Chamberlin & Ivie, C. coylei Bennett spec. nov., C. fraxineus Bennett spec. nov., and C. thermydrinos Bennett. All species have very restricted distributions on the western slopes of the central and southern Sierra Nevada mountain range in California from Tuolumne County south to northern Kern County (Figs 41–42).