Pupae were transferred individually to 5 ml glass vials filled with deionised water. The water was removed when imagines emerged. Imagines were held in the vials without access to food or water. Ambient temperature for pupae and imagines was the same as their respective larval rearing temperature. The relative humidity in the climate chambers and rooms (Additional file 1: Table S1) was kept at 90%. The age at pupation, age at emergence, age at adult death, adult sex and mortality were recorded, and the length of the R1 wing vein was measured as described in . To ensure that moribund larvae in the 0 °C treatment were dead, the cups were incubated at 10 °C for two days and then brought to 25 °C ambient temperature.