Oecobius Lucas, 1846

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 : 502-503

Genus: Oecobius Lucas, 1846

Type species: Clotho cellariorum Dugès, 1836 .

Remarks. The generic limits of Oecobius are problematic ( Shear 1970). Zamani et al. (2024) recently suggested that several species groups can be distinguished based primarily on the conformation of their copulatory organs, thus corroborating observations from previous studies of the genus; see discussion by Lehtinen (1967) and Shear (1970). Despite this, all species currently distributed in Mexico remain placed within Oecobius . This genus can be distinguished from Platoecobius Chamberlin & Ivie, 1935 , the only other genera found in the Americas, by having a moderately elevated pars cephalica and ocular area as long as, or longer than, wide ( Chamberlin & Ivie 1935; Santos & Gonzaga 2008).

Shear (1970) distinguished a group of Mexican species based on shared habitus coloration and similar copulatory organs morphology. Specifically, Shear (1970: 132) stated that O. rivula exemplifies this group by possessing a thick and robust radical apophysis (process of radix) and enlarged stipes positioned mesally. Jiménez & Llinas (2005) referred to the same structures as radix and terminal apophysis, respectively. Jiménez & Llinas (2005) observed a small basal protuberance on radix, which they labeled as radical apophysis, but it differs from the structure described by Shear (1970). Shear seemingly did not label this secondary apophysis on the radix. The only apparent point of agreement between Shear (1970) and Jiménez & Llinas (2005) concerns the conductor, described as a large and complex structure bearing apophyses and located ectally in the “Mexican” group.

Females within the “Mexican” group share a relatively long and broad scape. The fertilization tubes (sensu Shear 1970: 133) are visible through the integument and run anteriorly along the scape. Jiménez & Llinas (2005) referred to these structures as copulatory ducts, a term we consider more appropriate. The copulatory openings are located on or near the distal margin of the scape. Shear (1970) appears to have omitted a detailed examination of the vulva. This is evidenced by the lack of comment or illustration regarding the characteristic, weakly sclerotized, elongated, and globose sac observed in many Oecobius species. This sac, susceptible to collapsing after dissection, was labeled as spermathecae by Jiménez & Llinas (2005) and receptaculum by Baum (1972). Conversely, Shear (1970) identified structures with heavy walls as spermathecae, corresponding to the sclerotized capsule described by Baum (1972) and Jiménez & Llinas (2005). This capsule represents a sclerotized and expanded section of a duct, emerging posteriorly to the sac in O. rivula ( Baum 1972; 1980). Given that Baum (1972, 1980) provides a more comprehensive analysis of the vulval conformation in Oecobiidae , we consider the terms ‘capsule’ and ‘receptacle’ more appropriate for the time being.

Despite the relative complexity of the oecobiid male palps and epigynes, the species described below exhibit conspicuous differences in external characteristics, such as the radix and terminal apophyses, as well as the shape of the scape of the epigyne.

Composition of “Mexican” group: Oecobius culiacanensis Shear, 1970 , Oecobius culichi spec. nov., Oecobius hoffmannae Jiménez & Llinas, 2005 , Oecobius isolatoides Shear, 1970 , Oecobius isolatus Chamberlin, 1924 , Oecobius piaxtla Shear, 1970 , Oecobius rivula Shear, 1970 , Oecobius sudcaliforniana spec. nov., Oecobius yaqui spec. nov., and Oecobius yoreme spec. nov.

Distribution of “Mexican” group: Southwestern US (California and Arizona) and Northwestern Mexico (Baja California Sur, Sonora, and Sinaloa).