THERMOREGULATION IN UNPALATABLE DANAINE BUTTERFLIES

Thoracic temperatures of two species of unpalatable danaine butterflies in Papua New Guinea were high, exceeding ambient temperature on average by 5.5-degrees-C. Males and females of both species flew under conditions of intense solar irradiance, and in most cases showed significant regulation of thoracic temperature. Thoracic temperature excess was not, however, positively correlated with solar irradiance, body mass, or wing loading. In general, equilibrium temperature of a flying butterfly is influenced by choice of microhabitat, flight metabolism, and convective cooling. Interactions between these factors can be complex, and may alternatively result in thoracic temperatures close to ambient (as reported previously for unpalatable neotropical butterflies), or in a high thoracic excess, as exemplified by the danaine butterflies considered here. Association between palatability and thermal biology in butterflies thus has a variety of possible outcomes.