α‐Ecdysone does not induce ovarian development in adult Aedes aegypti

Abstract Previous findings have shown that vitellogenesis is initiated in non‐blood‐fed Aedes aegypti by injection of the insect steroid hormone ecdysterone. The precursor of ecdysterone, α‐ecdysone was assayed for its ability to induce ovarian development. Both the amount of vitellin deposited into ovarian follicles and the dopa decarboxylase activity were monitored. In contrast to ecdysterone, α‐ecdysone was negative with regard to both parameters. In addition, 22‐isoecdysone, previously reported to be active, was also shown to be ineffective. These findings suggest that the C20 hydroxylating mechanism necessary to convert α‐ecdysone to ecdysterone is absent in unfed females, but is activated by the blood‐meal.