Nesticus stygius Gertsch

Hedin, Marshal & DELLINGER, Bob, 2005, Descriptions of a new species and previously unknown males of Nesticus (Araneae: Nesticidae) from caves in Eastern North America, with comments on species rarity, Zootaxa 904, pp. 1-19 : 8-10

Nesticus stygius Gertsch 1984

Figs. 1, 11-12

Nesticus stygius Gertsch 1984: 36, figs. 170 -172.

Material Examined: Holotype. - Female, U.S.A: Tennessee: Overton County, Obe Lee Cave, coll. 21 December 1958, T.C. Barr, F. Breeding, & C. Kacsur (housed at AMNH).

Additional Type Locality Material Examined. - Male and female, U.S.A: Tennessee: Overton County, Obe Lee Cave, 36°12 ’23” N, 85°15 ’08” W, elev. ~ 400 meters, coll. 11 October 1993, M. Hedin & C. Phillips ( MCH male specimen #1882 ; MCH female specimen #1885 ).

Other Material Examined. - U.S.A: Tennessee: Overton County, Raven Bluff Cave, NW of Allons, 36°29 ’33” N, 85°21 ’36” W, elev. ~ 275 meters, coll. 1 October 1991, M. Hedin, K. Crandall & A. Gerber ( MCH female specimen #1018 ; MCH male specimens #1019 , #1020 ) .

Remarks. - Gertsch (1984) lists a female from Webb Cave, Putnam County, Tennessee. Webb Cave is actually in Overton County.

Diagnosis. - The troglomorphic features of N. stygius readily distinguish this species from smaller, surface-dwelling Nesticus found further east and north in the Appalachians. Compared to other large-bodied Appalachian troglomorphs, males of this species are distinguished by the unique shape of the dorsal paracymbial process (Fig. 11), and the distinctive thickened and chisel-like tegular apophysis (Fig. 12). The narrow median septum and bulging posteriolateral edges of the epigynum distinguish females (Gertsch 1984).

Description of male from type locality ( MCH male specimen #1882) (Figs. 11 & 12; Table 1). - Color of appendages and cephalothorax uniform in coloration, approximating HTML color "dark orange" (# FF 8 C 00). Abdomen darker, more flesh-colored, between "dark salmon" (# E 9967 A) and “gray” (#808080). Lenses of secondary eyes evident, without pigmentation. No external evidence of median eyes. Leg formula 1423. Legs very long, leg I over 11 times longer than carapace width. Paracymbium of male palpus with translucent dorsal process, bowed dorsally, forward, wide at base then narrowing towards tip, shaped like a duck’s head. Small paradistal process, distal paracymbium with fine serrations. Ventral paracymbium without modification. Tegular apophysis of palp well-sclerotized, thickened, blade-like, curving anteriorly. Small cuticular process arising near posterior origin of tegular apophysis. Median apophysis semi-translucent, approximately triangular, anterioromedial edge thickened.

Redescription of female from type locality ( MCH female specimen #1885) (Table 1). - Gertsch (1984) describes the holotype female as a "pale, eyeless, long-legged troglobite ", with "cephalothorax and appendages bright yellow, without pattern", "eyes obsolete or nearly so". The redescribed female is mostly consistent with this description, although coloration is not "bright yellow". Color of cephalothorax and legs similar to male, but with lighter, unpatterned abdomen. Lateral eyes only apparent as small patches of pearl-colored cuticle. No external evidence of median eyes. Leg formula 1423. Leg I almost 11 times longer than carapace width. Epigynum as illustrated by Gertsch (1984), with narrow median septum, pear-shaped anterior lateral fovea, posteriolateral edges thickened, rounded, and bulging conspicuously.

Variation. - Two males from Raven Bluff Cave, Overton County, Tennessee with paradistal process of paracymbium more pronounced, drawn into three-sided sharp point, otherwise similar to described male.

Natural History. - Both Obe Lee and Raven Bluff caves are moist caves, Raven Bluff with a small (permanent?) stream, Obe Lee with a wet weather stream that flows into the mouth. Spiders were found beyond the twilight zone in both caves, occupying vertically-oriented webs in relatively high humidity crevices along cave walls. A female collected on 1 October, 1991 from Raven Bluff Cave carried an eggsac containing 22 eggs.

Distribution. - This species is known only from four caves on the western margin of the Cumberland Plateau in Overton county, north-central Tennessee (Fig. 1).

DNA sequences. - Mitochondrial 16S (Genbank accession numbers AF 004648-49) and nuclear ITS ( AF 003817) DNA sequences were reported in Hedin (1997a).