Evidence of nest usurpation of Vespa velutina in the founding stage by V. basalis reveals it as a facultative social parasite (Hymenoptera, Vespidae)

Abstract

We investigated the usurpation behavior of the hornet Vespa basalis Smith in nests of V. velutina Lepeletier. We collected 47 nests of the two species in Taiwan in their establishment and growth stages. Of these, 29 were mixed-species nests, and in at least 16 V. velutina was replaced by V. basalis. While most nests were initiated by V. velutina, V. basalis coexisted with it during the establishment stage, leading to intense conflict between the two. The multiplex PCR method gave evidence of the usurper’s eggs and larvae in the mixed-species nest. Over time, the number of adults and brood in usurped V. velutina nests decreased, while those of V. basalis increased, demonstrating behavior in V. basalis akin to facultative social parasitism. This study provides further evidence of nest usurpation in the genus Vespa, along with description of complex interactions among these hornets, their natural enemies, prey, and humans in Taiwan.