Solitary Floral Specialists Do Not Respond to Cryptic Flower-Occupying Predators

Abstract

The impacts of predators on bee foraging behavior are varied, but have been suggested to depend on both the type of predator (namely their hunting strategy) and also risk assessment by the prey (i.e., ability to perceive predators and learn to avoid them). However, nearly all studies have explored these impacts using social bees, despite the fact that solitary bees are extremely diverse, often specialized in their floral interactions, and may exhibit different behaviors in response to flower-occupying predators. In this study, we examined foraging behaviors of wild solitary long-horned bees (Melissodes spp.) in response to a cryptic predator, the ambush bug (Phymata americana) on the bees’ primary floral host, the prairie sunflower (Helianthus petiolaris). We found sex-specific differences in foraging behaviors of bees, but little evidence that ambush bugs affected either pre-landing or post-landing foraging behaviors. Male bees visited flowers three times more often than females but female bees were five times more likely to land than males. Ambush bugs did not reduce visitation in either sex. Spectral analysis through a bee vision model indicated that ambush bug dorsal coloration was indistinguishable from the disc flowers of sunflowers, suggesting that ambush bugs are indeed cryptic and likely rarely detected by solitary bees. We discuss the implications of these findings for the perceived risk of predation in solitary bees and compare them to other studies of social bees.