Variation of thorax flight temperature among twenty Australian butterflies (Lepidoptera: Papilionidae, Nymphalidae, Pieridae, Hesperiidae, Lycaenidae)
Résumé
Thermal requirements for fl ight in butterfl ies is determined by a combination of external factors, behaviour and physical constraints. Thorax temperature of 152 butterfl ies was monitored with an infra-red thermometer in controlled laboratory conditions. The temperature at take-off varied from 13.4 degrees C, for a female Heteronympha merope to 46.3 degrees C, for a female Junonia villida. Heteronympha merope, an understorey species, had the lowest recorded take-off temperatures, with females fl ying at a much lower thorax temperatures than males. Among the tested butterfl y species, warming-up rate was positively correlated with take-off temperature and negatively with body mass. Wing loading is a major variable in determining the thorax fl ight temperature. Butterfl ies with the highest wing-loadings experienced the highest thorax temperatures at take-off. A notable exception to this rule is Trapezites symmomus, the only Hesperiidae of our data set, which had thorax fl ight temperatures of 31.5 degrees C and 34.5 degrees C, well within the range of the observed butterfl ies, despite a wing load ca. fi ve times higher. The high thorax temperature recorded in J. villida is probably linked to its high fl ight speed. The results highlight the importance of physical constraints such as body size on the thermal requirements for fl ight across a range of butterfl y species.
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licence : CC BY - Paternité
licence : CC BY - Paternité
