Hormonal Control of Ovary Development in Mosquitoes

Abstract

A study was made of ovary development in Culex pipiens form molestus Forskål, an autogenous mosquito not needing food in the adult stage to develop its eggs, and in C. pipiens pipiens L. and other anautogenous mosquitoes which require blood for ovary development. Comparison of the reserves of fully grown larvae of the autogenous and anautogenous forms of C. pipiens showed that the autogenous form had a rather larger fat body, but that the anautogenous form contained sufficient protein reserves to develop a number of eggs. It was considered that autogeny did not depend solely upon the ability to amass extensive reserves but also upon some other physiological mechanism. Decapitation and ligation at the base of the abdomen prevented ovary development in C. pipiens form molestus when performed within a few hours of emergence, but when performed 7 or more hours after emergence it often failed to prevent ovary development. It is suggested that a gonadotrophic hormone is secreted during this time. Ligation of the abdomen within an hour of feeding on blood appeared to prevent ovary development in Anopheles stephensi Liston. Ovary development occurred in a small proportion of females ligated 2 or more hours after feeding, and this proportion increased with time. Ligation of the abdomen immediately after blood feeding failed to prevent ovary development in Culex pipiens form berbericus Roubaud, Aëdes aegypti (L.) and Anopheles labranchiae atroparvus van Thiel, even in some cases where the ligature was tied within 2-3 min. of the start of feeding.