The basis of thermal melanism in the ladybird Adalia bipunctata: Differences in reflectance and thermal properties between the morphs

Abstract

The thermal properties of the red non-melanic and black melanic morphs of Adalia bipunctata were examined in the laboratory. Non-melanics have a higher cuticular reflectance than melanics. Under illumination similar to bright sunlight the temperature excess over ambient air (T. ex) gained by melanics is, on average, 2·1 °C larger than that of non-melanics. Initial rates of temperature change during heating and cooling are nearly 50 per cent faster for melanics. T. ex increases with weight in each morph class and is, on average, larger for females as these are larger. The larger melanics may have a higher risk of overheating than other Adalia in conditions of prolonged sunshine and very high ambient air temperatures. The results are discussed in relation to consequences of thermal melanism in natural populations and to the contribution of colour and size to insect heat budgets.