We report the water balance characteristics for diapausing and nondiapausing pupae of the flesh fly Sarcophaga crassipalpis. The challenge of maintaining water balance is particularly acute for pupae that spend 9–10 months in diapause, without access to drinking water. While diapausing pupae can tolerate a loss of up to 24.5% of their total body water content (67.3%), they have also acquired several other physiological attributes that have enhanced their capacity for maintaining water balance. Net transpiration rates for diapausing pupae (0.008 % h−1) are far lower than rates for nondiapausing pupae (0.023 % h−1). In addition, diapausing pupae can counter water loss with their ability to absorb water vapor from lower humidities (approximate water vapor activity, av, 0.58 at 20°C) than can nondiapausing pupae (approximate av 0.74 at 20°C). The high ritical transition temperature for diapausing pupae (39 °C, compared to 30 °C for nondiapausing pupae) suggests that epicuticular lipids have been modified to restrict water loss during diapause.

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