THE JUVENILE HORMONE. I. ENDOCRINE ACTIVITY OF THE CORPORA ALLATA OF THE ADULT CECROPIA SILKWORM

1. Juvenile hormone is secreted in high concentration by the corpora allata of the adult Cecropia moth.2. Notwithstanding this fact, the juvenile hormone has no apparent function in the adult moth. Extirpation of the corpora allata in the pupal stage fails to interfere with the production of normal moths whose gametes give rise to normal offspring.3. The corpora allata are inactive during the entire pupal stage as well as during the first two-thirds of adult development. If active corpora allata are implanted into a pupa just prior to the initiation of adult development, the juvenile hormone acts to oppose the differentiation of the adult moth. Development gives rise to an insect showing a mixture of pupal and adult characters. In the presence of high concentrations of juvenile hormone the pupa molts and transforms into a second pupa showing only traces of adult characters.4. The biological action of juvenile hormone is seen only in the presence of active prothoracic glands or their secretory product, ecdysone. Isolated pupal abdomens fail to respond to juvenile hormone unless ecdysone is simultaneously present. When both hormones are present, the pupal abdomen terminates diapause, molts, and transforms into a second pupal abdomen.5. Evidence is presented that the corpora allata secrete a factor which can mimic the brain hormone and activate the prothoracic glands. This finding is considered in relation to the endocrine control of larval molting.