The Effect of Peanut Oil on the Desiccation of Diapause and Postdiapause Pupae of the Moth, Callosamia promethea Drury

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Abstract
Normal diapause Promethea pupae lost weight over anhydrous CaCl2 at the same rate between the temperatures of 20[degree] and 35 [degree]C, regardless of saturation deficiency. Postdiapause pupae, under the same conditions, lost weight at a rate which is also independent of saturation deficiency but which is more rapid than that for diapause individuals. It is suggested that developing pupae produce more water as a result of their increased metabolism than is produced by diapause insects and that this water is lost by evaporation. The rate of weight loss of both normal diapause and postdiapause pupae is very slow. In the former group the weight at the end of 12 days" exposure to dry air was more than 95% of its original value, and in the latter group this value was approximately 85%. A single exposure of pupae to peanut oil results in a temporary increase in the rate of water loss, which is greater, the higher the saturation deficiency. However, after 3 or 4 days, the normal rate of dehydration is restored. This observation indicates that the hypodermis of the pupa is able to restore the water impermeability of the cuticle after its impairment by treatment with peanut oil. Successive daily treatments with peanut oil completely changes the permeability of the cuticle of the pupa so that, after two or three exposures, it becomes freely permeable to water. The rate of weight loss is then roughly proportional to the saturation deficiency of the air. It seems likely that the oil brings about its effect by dissolving a fatty or waxy substance from the surface of the cuticle.

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