Actinopus balcarce Ríos-Tamayo & Goloboff, 2018

Millenpeier, Micaela, Ferretti, Nelson Edgardo & Nicoletta, Micaela, 2023, Description of the female of Actinopus balcarce Ríos-Tamayo & Goloboff, 2018 (Araneae, Actinopodidae), with comments on its natural history, Journal of Insect Biodiversity and Systematics 9 (4), pp. 809-817 : 811-812

Actinopus balcarce Ríos-Tamayo & Goloboff, 2018 ( Figs 1–3)

Type material. Holotype ♂ (MACN-Ar2864): Argentina, Buenos Aires: Balcarce [ 37°51'S, 58°15'W] IV.1950, col. C. de la Serna (not examined).

Additional material examined. 1 ♀ ( UNS-M1056 ): Argentina, Buenos Aires: Balcarce, Sierra ‘ La Barrosa’ [ 37°52'28.8"S, 58°15'36.2"W] 28.IV.2023 , cols. Nicoletta & Schwerdt; 1 ♀ ( UNS-M1065 ): Argentina, Buenos Aires: Balcarce, Sierra ‘ La Barrosa’ [ 37°52'28.8"S, 58°15'36.2"W] 28.IV.2023 , cols. Nicoletta & Schwerdt; 1 juvenile ♀ ( UNS-M0571 ): Argentina, Buenos Aires: Balcarce, Sierra ‘ La Barrosa’ , 24.VI.2019, col. Ferretti ; 1 ♀ ( UNS-M661 ): Argentina, Buenos Aires: Olavarría , Sierras Bayas, no date, no collector ; 1 ♀ ( UNS-M1079 ): Argentina, Buenos Aires: Balcarce, Sierra ‘ La Barrosa’ , 21.IX.2023, col. Nicoletta.

Diagnosis. Females of A. balcarce can be distinguished from those of the congeners by the following combination of characteristics: sternum with a slight depression ( Fig. 2E); continuous thoracic fovea ( Fig. 2A); and sub-quadrate spermathecae with two receptacles bearing an external lobe well developed and projected in the same direction of the fundus or slightly twisted inwards ( Fig. 3A).

Description Female (UNS-M1056). Color (live specimen): Carapace and chelicerae dorsally black, abdomen dorsally dark grey; legs and palps with black femora and red patellae, tibiae, metatarsi and tarsi ( Figs 1A–1B, 1D). Color (in ethanol): Carapace black. Abdomen dark grey, booklungs with dark markings. Spinnerets yellowish. Sternum light brown, labium and maxillae dark brown. Coxae and femora black, patellae, tibia, metatarsi and tarsi reddish brown ( Figs 2A–2E). Total length: 23.38. Carapace: length 8.97, width 7.92, anterior part square and posterior part triangular ( Fig. 2A). Clypeus: length 0.67. Ocular group: length 2.27, width 4.14, anterior margin procurved and posterior margin recurved ( Fig. 2B). Eyes sizes and interdistances: AME 0.15, ALE 0.37, PME 0.23, PLE 0.34, AME–AME 0.42, AME–ALE 1.57, PME–PME 2.49, PME–PLE 0.23. Fovea: length 4.35. Chelicerae: length 5.39, width 2.99, with a total of 13 teeth. Rastellum: length 1.59; cuspules 44/41 ( Fig. 2C). Maxillae: cuspules 139/119 ( Fig. 2D). Labium: length 2.23, width 1.69, with 25 cuspules ( Fig. 2D). Sternum: length 6.30, width 5.34, with a slight central depression ( Fig. 2E). Sigillae: shallow, postlabial pair merged, subtriangular, first and second pair elongated, converging into the central depression; diameter: first pair 0.89, second pair 1.17, and third pair diameter 1.66; distances from the sternum edge: first pair 0.95, second pair 0.78, third pair 1.03 ( Fig. 2E). Abdomen: dorsal length 13.28, width 8.29; ventral length 11.15, width 8.08. Spinnerets: PMS length 0.96; PLS basal segment length 0.95, median 1.25, and apical 0.31. Spermathecae: length 1.09, width 0.59. Lengths of legs and palp: I: 4.54, 2.91, 2.65, 2.14, 1.5; II: 4.74, 2.87, 2.79, 2.78, 1.75; III: 5.09, 3.17, 1.91, 2.21, 1.84; IV: 5.61, 3.25, 3.71, 3.25, 2.19; palp: 4.08, 3.21, 3.65, 3.31; total lengths: I: 13.51, II: 13.61, III: 13.8, IV: 19.7, palp: 12.98. Chaetotaxy: All femora aspinose. Patellae: I, II 0; III 18p, 15d, 30r; IV 17p, 39r; palp 3p, 1v. Tibiae: I 5p, 21r, 3v; II 1p, 84r, 14v; III 19p, 12d, 45r; IV 37p, 37v; palp 11p, 38r, 1v. Metatarsi: I 13p, 21r, 5v; II 18p, 19r, 4v; III 38d, 45r, 3v; IV 22p, 1d, 1v. Tarsi: I 19p, 16r, 6v; II 15p, 4r, 10v; III 30p, 8d, 13r, 57v; IV 37p, 1d, 37v; palp 31p, 33r, 1v; claws 1p, 1r. Total number of retrolateral spines on tibiae I and II ( Fig. 2F): 21 and 84, respectively. Spermathecae: sub-quadrate, with two asymmetrical receptacles bearing an external constriction of the fundus that can be more or less prominent. The apical lobe is well developed and directed straight or slightly curved inwards; the inner and outer lobes are less developed and are projected perpendicular to the fundus axis ( Fig. 3A). Spermathecae variation: additional females examined (M1065, M661, M1079) have subtle differences in the spermathecae, such as a variation in the development of the internal lobe and the grade of inclination of the external lobe ( Fig. 3B).

Distribution. Argentina. Buenos Aires province: Sierra ‘La Barrosa’, Balcarce; New record: Sierras Bayas, Olavarría ( Fig. 1F).

Natural history. The burrows were found in the northern area of ‘La Barrosa’ hill, on a slope facing the northeast. The burrows were in bare ground and trap doors were covered with dirt and small pieces of plants ( Figs 1C–1D). The female (UNS-M1056) was inside a burrow of 20.8 mm of entrance diameter, with a lid of 25.5 mm in diameter and 3.86 mm in thickness. ‘La Barrosa’ hill is covered mainly with native plants representing the families Asteraceae (e.g., Bacharis and Senecio ) and Poaceae (e.g., Piptochaetium and Poa ); although, some alien plants were also found, e.g, Carduus , Senecio , Briza and Poa , among others ( Alonso et al., 2009).