Individual specialization on spider prey by the black and yellow mud dauber (Sceliphron caementarium)

Individual foraging specialization describes the phenomenon where individuals within a population of generalists exhibit differences in foraging behavior, each specializing on different prey types. Individual specialization is widespread in animals, yet is understudied in invertebrates, despite potential impacts to food web and population dynamics. Sceliphron caementarium (Hymenoptera: Sphecidae) is an excellent system to examine individual specialization. These mud-daubers capture and paralyze spiders to provision their offspring. Females may make hundreds of prey choices in their four-week lifespan and fully intact prey items can be easily excavated from their mud nests. Here we examined individual specialization in a population of S. caementarium in north central Florida. We collected 90 cells from the nests of 31 females from a bridge in Otter Creek, FL between May and July 2015. We identified all nest contents to the family level and analyzed the data using the R package, RInSp, which quantifies the level of individual specialization. Females took spiders from 10 families representing 5 ecological guilds that included both web-builders and non-web-builders. We found evidence for individual specialization in respect to both prey taxa and ecological guild. We found individual variation in the degree to which individuals were specializing with some individuals taking only spiders from a single family to others that took spiders from more than 5 families across a range of ecological guilds. We will discuss the implications of individual specialization in mud-daubers in the context of search image learning and the potential cascading impacts of predation on spiders.