Host-parasite interactions between Xenoglossa pruinosa (Apidae: Eucerini) and Triepeolus remigatus (Apidae: Epeolini) are characterized by tolerance and avoidance

Abstract In cleptoparasitic bees, host aggression and detection avoidance might be the main selective pressures shaping host-parasite interactions. However, the behavioral responses toward parasitism are unknown for most host species. In this study, we investigated the host-parasite interactions and behaviors of the cleptoparasitic bee Triepeolus remigatus when parasitizing the nests of its host, the squash bee Xenoglossa ( Peponapis ) pruinosa . Using circle-tube behavioral assays and direct observations at a nest aggregation of X. pruinosa , we assessed whether interactions between host and parasite were aggressive, tolerant, or avoidant and characterized the general parasitic behavior of T. remigatus . Our results reveal a lack of aggression between host and cuckoo bees, with interactions primarily characterized by tolerant and avoidant behaviors. Squash bees displayed minimal aggression toward both conspecifics and parasites. Interestingly, despite the absence of aggressive responses, T. remigatus preferred entering nests while the host was foraging, potentially indicating a strategy to avoid the discovery of parasitic visits. Furthermore, field observations provided insights into the parasitic behavior of T. remigatus , revealing primarily rapid visits to host nests without extensive inspection. The limited aggression and short time for nest visits observed in T. remigatus suggest adaptations to optimize parasitic success while minimizing host detection. Overall, our findings contribute to a better understanding of the behavior of open-cell parasites and provide a first accounting of the squash bee behavior when encountering parasitic bees. Further research is needed to elucidate the mechanisms underlying host-parasite coevolution and response to parasitism in ground-nesting bees.