Supporting data for "Distinct thermoregulatory strategies and challenges in subtropical butterflies and moths"

Temporal activity patterns expose animals to divergent thermal regimes and drive differences in their thermoregulation. In Lepidoptera (butterflies and moths), Clench discussed in his influential Ecology paper (1966) how diurnal butterflies and nocturnal moths may gain heat for activity in their respective thermal environments. However, this characterization may not be applicable across all ecosystems. We investigated the thermoregulation of butterflies and moths in subtropical Hong Kong through the measurements of field body temperature (Tb), operative temperature (Te) using felt models simulating lepidopteran insects, and set-point range (Tset) estimated by the preferred temperature in a laboratory thermal arena. Subtropical diurnal insects have to lose heat in the hot season, while minimal thermoregulation was needed for nocturnal insects. Through microclimate selection and postural adjustments within microhabitats, both groups exhibited the ability to regulate Tb under unfavorable temperatures towards their preferred Tset, which was not different between groups. Diurnal insects exhibited a heat threshold of 31.8 to 36.5°C, above which they buffered strongly against further increases in Tb. Nocturnal moths did not show constraints in raising their Tb, but also have limited thermoregulatory opportunities at night. Distinct thermoregulatory strategies may translate to distinct challenges for diurnal and nocturnal insects under climate change, further complicated by a diel asymmetry in warming trends and the changing availability of microclimates through large-scale habitat changes. A better understanding of thermoregulation in tropical insects is necessary for accurately characterizing vulnerabilities to climate change.