Oecobius isolatoides Shear, 1970

Alcántar-Valenzuela, Joel Jair, Chamé-Vázquez, David & Jiménez, María-Luisa, 2025, Four new species of the spider genus Oecobius Lucas, 1846 (Araneae: Oecobiidae) from northwestern Mexico, Zootaxa 5679 (4), pp. 501-520 : 514-518

Oecobius isolatoides Shear, 1970

Figs 51–60 , 73–75

Oecobius isolatoides Shear, 1970: 150 , figs 19, 37, 62–63 (Female holotype and male paratype from El Coyote, Sonora, deposited in the American Museum of Natural History; not examined). Baum 1980: 343, figs 10–12.

Material examined. MEXICO: Sinaloa, Ahome, Los Mochis in the Cerro of “La Memoria”(25.8130°N, 108.9697°W, 79 m), low tropical deciduous forest, manual collection, J. Alcántar leg., 19/VII/2022, 3♀ (CARCIB-Ar-5320); same data as for preceding, except (25.8128°N, 108.9684°W, 20 m), 18/VII/2022, 1♂ 3 juvs (CARCIB-Ar-5321); same data as for preceding, except (25.8100°N, 108.9712°W, 15 m), 18/XII/2021, 1♂ 5♀ 4 juvs (CARCIB-Ar-5322); same data as for preceding, except (25.8058°N, 108.9734°W, 21 m), 10/I/2022, 1♀ 15 juvs (CARCIB-Ar-4801); same data as for preceding, except (25.8093°N, 108.9714°W, 45 m), 05/I/2022, 1♂ 1♀ 8 juvs (CARCIB-Ar-4802); Cañón del Diablo , Sierra de Barobampo (26.0308°N, 109.0326°W, 94 m), low tropical deciduous forest, manual collection, J. Alcántar leg., 23/VII/2022, 1♂ 3♀ (CARCIB-Ar-4803); Choix, 2.36 km of La Estancia Baymena (26.5888°N, 108.2471°W, 448 m), riparian vegetation, manual collection, J. Alcántar leg., 25/VII/2022, 1♂ 7♀ 2 juvs (CARCIB-Ar-4799); same data as for preceding, except (26.5900°N, 108.2494°W, 422 m), 2♀ 7 juvs (CARCIB-Ar-4800); San Javier (26.6726°N, 108.4571°W, 223 m), house walls, manual collection, J. Alcántar leg., 13/IV/2022, 2♂ 1 juv. (CARCIB-Ar-5323) ; Sonora, Arizpe, Rancho “Las Playitas II”, 14.75 km of Bacoachi (30.5690°N, 110.1041°W, 1,138 m), xerophyte scrub, manual collection. J. Alcántar, K. Gómez leg., 18/IV/2022, 1♂ (CARCIB-Ar-4804); Cañón “Las Paredcitas”, Rancho “Las Playitas I”, 17.83 km of Bacoachi (30.5554°N, 110.1323°W, 1,071 m), riparian vegetation, manual collection, J. Alcántar, D. Chamé, K. Gómez, C. Palacios leg., 20/IV/2022, 1♂ 9♀ 1 juv. (CARCIB-Ar-4805) .

Diagnosis. The male palp of O. isolatoides resembles that in O. sudcaliforniana spec. nov., by having a rectangular radical apophysis shorter than the curved and pointed terminal apophysis; however, O. isolatoides lacks a membrane on radical apophysis ( Figs 55, 56 , Shear 1970: fig. 63; vs. membrane present in O. sudcaliforniana spec. nov., Figs 15–17 ), and the conductor bears one long, hyaline process ( Fig 57 , Shear 1970: fig. 62; vs. conductor bears three apophysis in O. sudcaliforniana spec. nov., Fig. 17 ). Females of O. isolatoides resemble those of O. isolatus by having the scape longer than wide; however, in O. isolatoides , the width of the apex of the scape is about one-third of scape base width ( Fig. 58 , Shear 1970: fig. 37; vs. about half of scape base width, Shear 1970: fig. 35).

Complementary description. Male palp. In prolateral view, radical apophysis rectangular (see variation section below); radical protrusion short and pointed; terminal apophysis curved upward and concave ( Fig. 55 ). Conductor with one hyaline process directed ventrad; embolus tubiform, curved, sclerotized, directed ventrad ( Fig. 57 ).

Epigyne. Scape slightly longer than wide (about 1.3 longer than wide), apex width about one third of base width; copulatory openings situated in apex of scape ( Fig. 58 ). Vulva . Copulatory ducts tubiform, directed anteriorly then arched laterally toward receptacles; sclerotized capsules small, elongated; receptacles hyaline and globose; blind appendix reniform, restricted to posterior third of the epigynal length ( Fig. 60 ).

Variation. The coloration of females is usually darker than males. The number of white spots on opisthosoma venter varies, but females generally have a reduced number of white spots. A male specimen (CARCIB-Ar-4799) exhibits a more protruding lower edge of the radical apophysis on left palp ( Fig. 56 ) compared to other specimens from Sinaloa and Sonora assigned to the same species. Additionally, this specimen has a hyaline process that is basally wider than those observed in other specimens. The right palp of same specimen matches the images of Shear (1970). Females within the same specimen batch (CARCIB-Ar-4799) exhibit sclerotized capsules, ranging from slightly discernible to clearly visible through integument.

Natural history. In Sinaloa, specimens of this species were frequently found under rocks in riparian vegetation, xerophyte scrub, and tropical deciduous forest. In Sonora, they were found on canyon walls, up to four meters from the ground, with webs placed following an active ant path. Adult specimens were collected in January , April , July , and December. Three round ovisacs with 6 to 7 eggs were found in January and July of 2022 (N=3). Furthermore, this species has a wide altitudinal range and can be found from 15 to 1,138 meters above sea level .

Distribution. Known only from southern Arizona ( U.S.A.), Sonora, and Sinaloa ( Mexico) ( Shear 1970); see Fig. 76 .

Figures

FIGURE 76. Distribution of Oecobius species based on records from the current paper, Shear (1970), and Jiménez & Llinas (2005).

FIGURES 51–60. Oecobius isolatoides. 51. male habitus, dorsal; 52. same, ventral; 53. female habitus, dorsal; 54. same, ventral; 55. male palp, prolateral; 56. same, ventral; 57. same, retrolateral; 58. epigyne, ventral; 59. cleared epigyne, ventral; 60. same, dorsal. Scale bars 51–54: 1.0 mm; 55–57: 0.30 mm; 58–60: 0.10 mm. Abbreviations: BA—blind appendix; C— conductor; CD—copulatory ducts; CO—copulatory openings; E—embolus; FD—fertilization ducts; K—sclerotized capsule; R—receptacle; RA—radical apophysis; TA—terminal apophysis.

FIGURES 70–75. 70–72. Oecobius hoffmannae. 73–75. O. isolatoides. 70, 73. male palp, prolateral. 71, 74. Same, ventral. 72, 75. Same, retrolateral. Scale bars 70–75: 0.10 mm. The processes of the conductor are color-coded as follows: green for the subapical process, red for the median process, and blue for the subbasal process. Abbreviations: C—conductor; E—embolus; RA—radical apophysis; RP—radical protrusion; TA—terminal apophysis.

FIGURES 11–20. Oecobius sudcaliforniana spec. nov. 11. male habitus, dorsal; 12. same, ventral; 13. female habitus, dorsal; 14. same, ventral; 15. male palp, prolateral; 16. same, ventral; 17. same, retrolateral; 18. epigyne, ventral; 19. cleared epigyne, ventral; 20. same, dorsal. White arrows point hyaline membrane in Figs. 15–17. Scale bars 11–14: 1.0 mm; 15–17: 0.30 mm; 18–20: 0.10 mm. Abbreviations: BA—blind appendix; C—conductor; CD—copulatory ducts; CO—copulatory openings; E— embolus; FD—fertilization ducts; K—sclerotized capsule; R—receptacle; RA—radical apophysis; TA—terminal apophysis.