Relation between Lipid Content of Cuticle, Duration of Diapause, and Resistance to Desiccation of Pupae of the Cynthia Moth

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Abstract
Cynthia pupae were rolled on filter paper moistened with peanut oil until the cuticle was thoroughly coated with the oil. At the end of 10 min. the oil was cleaned from the surface and the pupae were placed in desiccators at different humidities. Other pupae were immersed in ether for varying periods of time and then exposed to different humidities. Such treatments increased the permeability of the cuticle to water but had no effect on the duration of diapause. Long exposures to ether removed more lipid from the cuticle than short exposures and increased the rate of water loss at low humidities. Normal diapausing pupae lost wt. at a very slow rate at 25 C, regardless of saturation deficiency, the loss in dry air amounting to only 3% of the original wt. during a 50-day period. However, the wt. loss of diapausing pupae treated with peanut oil or ether was very rapid at low humidities and was proportional to the saturation deficiency. The film of lipid on the surface of the cuticle protects the pupa from dehydration and from attacks by parasitic fungi.