The relative importance of the avenues of water gain discussed below depends largely on the availablity of water in the insect's environment. An extreme example is seen in stored products insects which live in an atmosphere of low av, have no access to free water, and consume food of minimal water content (varying with ambient av). Periods of fasting may be necessary to survive such conditions (Arlian 1979). Higher av enables feeding to continue, but adults of Sitophilus granarius (Coleoptera, Curculionidae) consuming tapioca at an av of 0.8 gain much more water from metabolism and from passive vapour absorption than from the food itself (Devine 1978).
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