Avian Predation Impacts on a Deep Cave-Nesting Population of Ageniella evansi in Arizona, USA

Abstract

The findings of an ongoing long-term study of deep cave-nesting populations of the spider wasp Ageniella evansi Townes, 1957 (Hymenoptera: Pompilidae) were recently published (Pape 2024). The populations of wasps nest deep within the limestone caves at Colossal Cave Mountain Park near Tucson, Arizona, USA. The cave nesting behavior of these populations is unique within the Pompilidae. These wasps are active from November through April, which is unusual among the Nearctic members of this family. This study focused on the primary population of these wasps, which occupy Arkenstone Cave. The effects of predation on the wasp population were reviewed in the original study, but recently, a Rufous-crowned Sparrow (Aimophila ruficeps Cassin, 1852) was observed preying on one of the wasps. This confirmed a suspected association between these two species and is discussed in this study. The annual decrease of the wasp population in December and January each year now seems like it could be attributed to this predation. The total impacts of avian predation on the wasp population are detrimental, but they are considered unlikely to result in a significant diminution or extirpation of the wasp population.