Abstract
To assess the role of the cocoon in protecting against desiccation, the effect of humidity on naked pupa of the braconid parasitoid wasp, Cotesia glomerata L., was investigated. Daily weight changes of the intact cocoon showed that the parasitoid lost more than half its body weight during development in the cocoon (20°C, 16L: 8D), and suggested that it would suffer severe dehydration at the time of pupal and adult eclosion. The survival rates of naked pupae kept at 100, 75, and 50% RH (20°C, 16L:8D) were 69, 44, and 32%, respectively. When naked pupae were maintained in an open, sunny location, no active adults emerged, and even when maintained in an open, shaded location only one fourth of the parasitoids completed development. The survival rate at 100% RH was significantly higher than that under the other experimental conditions (p < 0.01). Over 95% of intact cocoons kept at 50% RH or in the sunny location showed successful emergence. The cocoon of C. glomerata effectively protected the prasitoid from desiccation even at moderate ambient relative humidity.
