Open Access

Frank E. Kurczewski

• A first-time analysis of taxonomically relevant characters, functional morphology, geographic distribution, ecoregion preference, and hypothetical host spiders of Pepsis basifusca Lucas (Hymenoptera: Pompilidae: Pepsinae) is presented. This analysis is compared with other Nearctic species in Vardy’s (2005) Pepsis menechma species-group, particularly P. cerberus Lucas and P. elegans Lepeletier which are suspected parasitoids of trapdoor spiders. Pepsis basifusca females differ from females of these species in possessing a rounded gena-postgena in dorsal view; straight mid and hind tibial spurs; short hind tibial inner spur; and short, very stout, and backward slanted hind tibial bristles. Pepsis basifusca Level III Ecoregions comprise mountains, plateaus, highlands, and tablelands, often at high elevation (~3,000–5,000 feet (914–1,524 meters), from Utah, Colorado, Kansas, and Missouri to Panama. Pepsis basifusca, the smallest Nearctic congener, should be expected to capture comparatively small mygalomorph spiders like some other species in Vardy’s (2005) Pepsis menechma species-group. Based on taxonomic, morphological, biogeographical, and potential host spider criteria, P. basifusca should probably be removed from this group and transferred to another species-group. ZooBank registration. urn:lsid:zoobank.org:pub:4D3BF37C-3358-4C25-B56A-104C57301AE2