Puparial wax restricts passive movement of water during diapause in the flesh fly

. To determine whether the capacity of diapausing pupae of the flesh fly ( Sarcophaga crassipalpis Macquart) to absorb water from drier air than non‐diapausing pupae is due to a simple passive process, we examined water flux in empty puparia. Empty puparia from both types of fly absorb and lose water passively, but those from diapause pupae do so to a lesser degree. The impervious nature of such puparia is attributed to an extra layer of cuticular wax not found in the non‐diapause group.