Genus Oxyrrhexis Förster, 1869

Oxyrrhexis Förster 1869: 166 . Type species: Cryptus carbonator Gravenhorst, 1807, by monotypy (Schmiedeknecht 1888: 432; see also Perkins 1962: 441).

References. Viereck 1914: 108 [syn. of Acrodactyla]. Townes & Townes 1960: 242 [description; 1 species in Nearctic region]. Townes 1969: 106 [diagnosis]. Carlson 1979: 336 [catalogue; 1 species in North America]. Gauld & Dubois 2006: 552 [description; Holarctic genus with 2 species]. Liu et al. 2009 [review of 3 species from China (2 described as new); key]. Fritzén & Fjellberg 2014 [review; 1 new species from Norway; host, biology].

Oxyrrhexis is a small genus with four species: two species in Eastern Palaearctic region and Oriental China, one recently described species from Norway (Fritzén & Fjellberg 2014), and one widely distributed Holarctic species, O. carbonator . The latter species, as well as the genus Oxyrrhexis, is recorded here from Mexico for the first time.

Oxyrrhexis is very similar to Polysphincta, but differs from this genus by the shorter ovipositor and more densely and coarsely punctate metasomal tergites (Townes & Townes 1960; Townes 1969). Three Costa Rican species of Polysphincta also possess a rather short ovipositor and their generic placement may need to be reassigned (Gauld 1991: 308).

Species of Oxyrrhexis are koinobiont ectoparasitoids of adult spiders. Fritzén & Fjellberg (2014) supposed that Oxyrrhexis is a genus specialized on spiders of Theridiidae and might be restricted to only two theridiid genera, Steatoda Sundevall and Enoplognatha Pavesi, or to subfamilies Asageninae, Enoplognathinae and less likely also Theridiinae.