The influence of the brain hormone on retention of blood in the mid-gut of the mosquito Aedes aegypti (L.) III. The involvement of the ovaries and ecdysone

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Abstract
Most female mosquitoes require a blood-meal to produce mature oocytes. An egg development neurosecretory hormone (EDNH), which is produced in the medial neurosecretory cells (m.n.c.) of the brain and stored in the corpus cardiacum, is released into the hemolymph following the ingestion of blood and is essential for the promotion of ovarian development to maturity. A factor from the m.n.c., presumably EDNH, is necessary if the blood-meal is to be retained in the mid-gut until the oocytes approach maturity. Retention is not a direct result of the action of EDNH, but is dependent on the ovaries and may well involve ecdysone. Removal of the ovaries before a blood-meal leads to early hemdefecation, but delay can be restored by injection of ecdysterone. Sub-threshold feeders and mosquitoes decapitated immediately after the intake of blood, each of which would be expected to eliminate the blood-meal early, also show a delay in the onset of hemdefecation when injected with ecdysterone. In both ovariectomized insects and sub-threshold feeders the time of onset of hemdefecation is associated with the dose of ecdysterone given.