Hagenius brevistylus lost mass by evaporation in a moderately desiccating environment at the rate of 20.4 mg/h, and died of desiccation in less than 1 day at a body mass of 79.8% of their normally hydrated mass. It was estimated that Hagenius minimally would have to consume the equivalent of 60% of its body mass each day to meet its daily water requirements. This amount of food is equivalent to that necessary to power flight of a dragonfly for 4.6 h.