Thermoregulatory behavior and fungal infection of Anoplophora glabripennis (Coleoptera: Cerambycidae).

Asian longhorned beetles, Anoplophora glabripennis (Motschulsky), are invasive wood borers that are native to China and Korea but have been introduced to North America and Europe. These beetles have great potential to negatively impact economic and environmental interests in hardwood and urban forests if they become established. The entomopathogenic fungus Metarhizium brunneum Petch (previously Metarhizium anisopliae (Metschnikoff) Sorokin) is under development for control of A. glabripennis. Some insect species eliminate pathogens or delay disease progression through thermoregulation. Because Asian longhorned beetles had been observed occupying sunlit areas of the tree canopy, we hypothesized that behavioral fevering could be used to delay mortality of fungal-infected beetles. M. brunneum cultures incubated at 34°C for 5 h/d grew significantly slower compared with cultures incubated at lower temperatures. Holding M. brunneum-infected A. glabripennis at 34°C for 5 h/d significantly delayed mortality by 2 d compared with infected beetles held at ≤31°C. Adult A. glabripennis did not exhibit behavioral fever when infected. Uninfected males, when provided with food, and both uninfected males and females when deprived of food, slightly increased their preferred temperature over time. When held at 15°C before being placed into temperature gradients, uninfected beetles did not increase their temperatures above ambient. Results demonstrate that M. brunneum-infected A. glabripennis do not exhibit behaviors necessary to elevate their body temperatures enough to combat M. brunneum infections through thermoregulation.