Ecdysone stimulates and juvenile hormone inhibits follicle formation in a gall midge ovary in vitro

The larval ovaries of the paedogenetic gall midge Heteropeza pygmaea can be cultured in vitro throughout oögenesis. Addition of farnesol or C₁₆ juvenile hormone to the culture medium inhibits follicle formation in the ovaries; addition of ecdysterone, on the other hand, strongly accelerates the formation of follicles. It is suggested that ecdysone triggers or stimulates follicle formation in the ovaries also in vivo, and that juvenile hormone acts on oögenesis in a later stage of development.