Larval-Pupal Transformation: Control by Juvenile Hormone

Purified extract of juvenile hormone from the cecropia silkmoth prevents the transformation of larva to pupa in Galleria . The injected extract acts independently of the insect's own corpora allata. A morphological response occurs only when juvenile hormone remains in the body from the time of injection until the end of the period in which any cells are still sensitive to the hormone. The extent of the effect depends upon the age at which the larva receives the injection. The maximum effect (perfect superlarva) is produced when the extract is provided not later than in the first third of the instar.