Gathering in an empty house: Arthropod assemblages overwintering in abandoned hornet nests

Abstract

AbstractAlthough some species of hornets spend enormous amounts of time constructing their nests, they only utilize the nest for one season and abandon it to overwinter in other habitats. Abandoned nests may be attractive habitats for other organisms to avoid predators and bad weather, but our knowledge of the organisms that make use of hornet nests for overwintering is very limited. Here, we examined the secondary inhabitants of abandoned winter hornet nests in northern part of Japan. A total of 96 live arthropods (5 orders, 23 species) were collected from six nests and were dominated by Araneae (85.4%). Our finding suggests that hornet nests serve as overwintering sites for many other organisms and that hornets may act as physical ecosystem engineers by creating overwintering habitats for other arthropods (mostly spiders). We predict that abandoned nests indirectly affect the prey community structure on trees, by providing overwintering sites for predatory spiders. In addition, reduced snow cover due to global warming may prevent nest collapse and enhance the ecological functioning of hornet nests. We emphasize that hornet nests present an ideal system for assessing how climate change alters communities through its effect on engineered structures. Further studies are required to clarify the role of hornets as ecosystem engineers among tree communities in fluctuating environments.