With climate change creating a more volatile atmosphere, heatwaves will become stronger and more frequent, influencing living systems. Using the flour beetle Tribolium castaneum, we measure the impacts of experimental heatwaves on reproduction and survival across different insect life stages, and the extent and pace of any recovery. We exposed larvae, pupae, juvenile and mature adult male beetles to 5-day heatwaves at 40°C or 42°C, a few degrees above the 35°C optimum for this species’ population productivity, and then measured survival and reproduction. Heatwave-induced mortality was greatest among juvenile life stages. Male reproductive function was specifically damaged by heatwaves, especially if experienced through pupal or immature life stages when complete sterility was shown at reproductive maturity; larval exposure did not damage adult male fertility. Heatwaves impaired testis development and the production of viable sperm, with damage being strongest when experienced during pupal or juvenile adult stages. Despite this disruption, males recovered from heatwaves and, depending on the stage of exposure, testis size, sperm production and fertility returned to normal 15 to 28 days after exposure. Our experiments reveal how extreme weather could impact on insect survival and reproduction across different life stages, and the potential and timescales of recovery.

 Raw data, code and figures for analysis in R.