title: Differences in heat sensitivity between Japanese honeybees and hornets under high carbon dioxide and humidity conditions inside bee balls.
abstract: Upon capture in a bee ball (i.e., a dense cluster of Japanese honeybees forms in response to a predatory attack), an Asian giant hornet causes a rapid increase in temperature, carbon dioxide (CO₂), and humidity. Within five min after capture, the temperature reaches 46°C, and the CO₂ concentration reaches 4%. Relative humidity gradually rises to 90% or above in 3 to 4 min. The hornet dies within 10 min of its capture in the bee ball. To investigate the effect of temperature, CO₂, and humidity on hornet mortality, we determined the lethal temperature of hornets exposed for 10 min to different humidity and CO₂/O₂ (oxygen) levels. In expiratory air (3.7% CO₂), the lethal temperature was ≥ 2° lower than that in normal air. The four hornet species used in this experiment died at 44-46°C under these conditions. Hornet death at low temperatures results from an increase in CO₂ level in bee balls. Japanese honeybees generate heat by intense respiration, as an overwintering strategy, which produces a high CO₂ and humidity environment and maintains a tighter bee ball. European honeybees are usually killed in the habitat of hornets. In contrast, Japanese honeybees kill hornets without sacrificing themselves by using heat and respiration by-products and forming tight bee balls.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Bioenvironmental Science, Kyoto Gakuen University, 1-1 Nanjo-Ohtani, Sogabe-cho, Kameoka, Kyoto 621-8555, Japan. sm1295@nifty.com
authors.forename: Michio
authors.initials: M
authors.lastname: Sugahara
authors.forename: Yasuichiro
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Fumio
authors.initials: F
authors.lastname: Sakamoto
mesh_terms: D000818:Animals; D001516:Bees / Q000502:physiology*; D001522:Behavior, Animal; D002245:Carbon Dioxide / Q000494:pharmacology*; D006358:Hot Temperature; D006813:Humidity; D012919:Social Behavior; D014863:Wasps / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide