Seasonal changes in the territorial behaviour of the satyrine butterfly Lethe diana are mediated by temperature

Abstract

The territorial behaviour of butterflies often changes with temperature. The satyrine butterfly Lethe diana has three generations a year, and males display territorial behaviour in the May–June and September–October generations, but not in the July–August generation. This study investigated the relationship between this seasonal change in mate-locating behaviour and thermoregulation. When L. diana was able to hold a territory, thoracic temperature ranged from 23.8 to 33.6°C. This temperature was mainly influenced by environmental temperature based on air temperature, solar radiation, and wind, and metabolic heat was estimated to increase thoracic temperature by about 5°C in the May–June generation. When environmental temperature at a territorial site was within this range of the thoracic temperature minus the metabolic heat (approximately 5°C), L. diana males held territories. Since territorial sites were selected irrespective of the temperature, L. diana could not hold a territory when the temperature of the territorial site exceeded the threshold. In July–August, the temperature of the territorial site was almost always above the suitable range. These results suggest that seasonal change in territoriality of L. diana is due to behavioural thermoregulation.