A hormone secreted by insects which inhibits the molting of an insect from its juvenile into its adult form; also, substances having similar activity, but produced by plants.

A chemical produced by the corpora allata, one of the three major insect development hormones, and responsible for determining the type of moult which will occur when one is directed by ecdysone. At high JH blood titre, additional larval or nymphal moults occur; low titre or complete absence of JH causes the pupal or imaginal transformation to occur.

hormone released by the corpora allata into the haemolymph. Juvenile hormone suppresses the development of adult characters and the amount of juvenile hormone released determines the outcome of a moult. View image