Critical thermal limits
We quantified critical thermal limits in virgin flies 8-10 days old,
using the dynamic method (Bozinovic et al. , 2016), which involves
heating or cooling flies from a starting temperature until physiological
failure (Terblanche et al. , 2007). Flies were placed individually
in 5 mL glass vials into a thermoregulated bath, and the temperature was
monitored employing a type K thermocouple inserted into a control empty
vial. The flies were allowed to equilibrate for 10 min at either 19 or
28 °C before either CTmin orCTmax assessments started, respectively. The
cooling and heating rate were 0.1 °C min °C−1. We
monitored flies every minute and recorded thermal limits as the
temperature when postural control was lost. The point of critical
thermal minimum (CTmin ) was defined as the
temperature of loss of a coordinated muscle function, and critical
thermal maximum (CTmax ) was defined as the
temperature of onset of muscle spasms as suggested by Terblancheet al. (2007)