Drymusa serrana Goloboff & Ramírez, 1991

Labarque, Facundo M. & Ramírez, Martín J., 2007, Description of the female of Drymusa serrana Goloboff & Ramírez, 1991 (Araneae: Drymusidae) with notes on its biology, Zootaxa 1580, pp. 27-33 : 28-31

Drymusa serrana Goloboff & Ramírez, 1991

( Figs. 1–23)

Type. Male holotype (MACN-Ar 8752) from Argentina, Buenos Aires Province, Sierra de la Ventana , Oct. 1980, P. Goloboff and A. Zanetic cols., examined .

Other examined material. Argentina: Buenos Aires Province: Sierra de la Ventana, Parque Provincial Ernesto Tornquist, Cueva del Toro (38º 1.142' S; 62º 0.97' W), 10 Jan 2005, G. Binford, J. Miller, F. Labarque and C. Ellison cols., 1♀ (MACN-Ar 11017), 2♀ (MACN-Ar 11018, 11020), 1 penultimate ♀ (MACN-Ar 11019), 2♂ (MACN-Ar 11021, 11022); same data as holotype, 4 immatures (MACN-Ar 8754); same locality, 26 May 1990, Anghilante col., 1 immature (MACN-Ar 11023); Oct–Nov 1964, Gallardo col., 1 immature (MACN-Ar 11024) . San Luis Province: Merlo (32º 21.434' S; 64º 56.786' W), 31 Dec 2004, G. Binford, J. Miller, F. Labarque and C. Ellison cols., 2♀ (MACN-Ar 11012, 11015), 2 penultimate ♀ (MACN-Ar 11013, 11016), 3♂ (MACN-Ar 10790, 11011, 11014); Villa Elena, 10–11 Nov 1982, E. Maury col., 1 immature (MACN-Ar 8789) .

Diagnosis. The female of D. serrana is distinguished from the other species by the presence of two sclerotized lips on the epigastric furrow ( Figs. 4–6, 8) and spermathecae with tubular receptacula associated ( Figs. 9–14).

Description of female (MACN-Ar 11017): Carapace orange slightly darker at margins, with two brownish dark spots forming a "V" and three lateral radial lines ( Figs. 1, 7), darker zones with thicker setae. Eye area brownish. Abdomen gray with brownish chevron, cardiac area dark ( Figs. 1–3, 7). Total length, 10.76. Cephalothorax 4.80 long, 3.72 wide, low and flattened, without fovea. Chelicerae with two teeth and a lamina in the promargin and two small teeth in the retromargin; fangs short, stout, curved. Endites elongated, converging in front of the labium, with fleshy apical edge. Labium 1.36 long, 1.02 wide, separated from sternum by a suture. Sternum 2.22 long, 1.90 wide, rounded posteriorly. Leg measurements: Femur: I: 12.06, II: 10.43, III: 7.82, IV: 10.43; Patella: I: 1.50, II: 1.44, III: 1.34, IV: 1.20; Tibia: I: 11.90, II: 10.11, III: 7.34, IV: 9.78; Metatarsus: I: 11.74, II: 9.78, III: 7.34, IV: 9.78; Tarsus: I: 2.14, II: 1.90, III: 1.64, IV: 2.12; Total: I: 39.34, II: 33.66, III: 25.47, IV: 33.31. Tibiae and metatarsi without recurved setae, only with filiform and spiniform setae. Tarsi long and thin, ventral face with abundant setae, with thick setae beneath third claw, and well developed onychium. The superior claws of the anterior two pairs of legs with a double row of teeth on the ventral surface of the proclaw and a single row on the retroclaw. Paired claws of tarsi I with 15 teeth and of tarsi IV with 19.

Abdomen elongated, posteriorly acute; without cuticular wrinkles. Colulus evident. Spinnerets arrangement: Anterior lateral spinnerets with two major ampullate gland spigots, posterior spigot smaller; posterior median spinnerets with a field of spicules on the median surface and posterior lateral spinnerets with several spigots.

Genital area with a raised lip posterior to the epigastric furrow, more sclerotized at the sides, bearing thick setae; without sclerotized plates ( Fig 4–6, 8) around genital area. Vulva with a pair of small oval spermathecae, irregular or tetrahedral, with or without one to three tubular receptacleson each side ( Figs. 9-11). The number and presences of tubular receptacles are variable in other females, often asymmetrical ( Figs. 12–14).

Variation. Females (n = 6). Total length 10.76–9.70. Cephalothorax, 4.80-4.12 long, 3.72–3.00 wide. Femur I: 12.06–9.05. The extremes are specimens MACN-Ar 11017 (larger) and MACN-Ar 11015 (smaller). Internal genital area differs between specimens. Spermathecaes can be oval, tetrahedral, or more irregular and tubular receptacles could differ in shape and number, sometimes absent on one or both sides ( Figs. 9–14). Males (n = 6). Total length 9.13–6.30. Cephalothorax, 3.72–2.68 long, 3.16–2.12 wide. Femur I: 13.69–8.08. Measurements from specimens MACN-Ar 11022 (larger) and MACN-Ar 11014 (smaller).

Description of egg-sacs. Here we described the egg-sacs of D. serrana for the first time. We found four egg-sacs in total, each of them associated with a female, in a superficial cavity (Cueva del Toro). One of them was not accessible for collection (but was photographed, see Fig. 19). One egg-sac contained 41 eggs, the other two 78 and 51 spiderlings. The egg-sacs are spherical to oval in shape, larger than the female body. The internal silk lining is white, finely meshed, and the external surface is covered with debris, like prey remains, pieces of exuviae, pieces of leaves, and other detritus. The sacs were found hanging on the webs, attached by several threads ( Figs. 16–19).

Description of web. The webs of D. serrana were found attached to large supporting objects such as the crevices in the cave’s walls ( Figs. 15, 19) or under rocks ( Figs. 21–22). The spiders rested on the underside of the web ( Figs. 15, 16) and also layed their eggs there ( Figs. 16–19). The lines in the sheet were not arranged in geometrically regular arrays; there were straight lines under tension (arrows T, Figs. 15, 20–22), connected by loose lines that sagged when dusted with cornstarch (arrows L, Figs. 15, 20, 22). The tense lines have multiple anchor points attaching to the surface (arrows B, Figs. 20, 23). We also found a web with a deviating sort of pattern ( Fig. 23) under rocks, parallel to the surface.

Natural history. The male holotype was found near the Cerro de La Ventana (Buenos Aires Province, Argentina), under big rocks in stream creeks ( Goloboff & Ramirez, 1991). The new specimens collected in Sierra de La Ventana were found inside a shallow cavity, Cueva del Toro , at 565 meters of elevation, near the type locality. The cave has an entrance of six meters in diameter that drops 10 meters before choking off. The spiders were hanging in their webs, more or less at a distance of one meter from the ground, between the crevices of the wall ( Figs. 15–16, 19). All the samples were found in the inner half of the cave, which was wetter and darker than the outer half. These spiders were larger than the male holotype and also than the specimens from Merlo , San Luis Province. The specimens from Merlo were collected under a pile of rocks mixed with soil, covering tree roots inside an old construction without roof made with those rocks. The spiders were hanging in their webs at the inner side of the rocks ( Figs. 21–22), where they moved quickly and gracefully .