Heat phase duration in diel temperature cycles affects survival and fertility of diamondback moth

With global climate change, the intensity and frequency of thermal extreme events are increasing. It is crucial to study the effects of environmental fluctuations and stressful temperatures on insects, which are small ectotherms. However, the impact of the temporal proportion of extreme heat exposure within diel cycles on insects remains poorly understood. To define the effect of different temporal proportions of a permissively stressful temperature 34 °C, and an optimal temperature 24 °C, on the performance of Plutella xylostella L. (Lepidoptera: Plutellidae) in diel cycles, we used the 2 temperature phases to study the effect of heat phase duration (0 h, 6 h, 12 h, 18 h, 24 h) on P. xylostella. The results showed that the developmental durations of individual life cycles were significantly shorter with longer heat phases. The life span of the adult was significantly shorter, and pupa weight was significantly reduced with increasing duration of the heat phase. Eggs of all female adults were unable to hatch in the 18 h heat treatment. This study provides critical insights into the temporally scaled impacts of extreme heat on insects under rapid climate change.