Induction of supernumerary moults in Galleria mellonella: Evidence for an allatotropic function of the brain

Implantation of brains from chilled Galleria larvae into first-day last-instar host larvae results in a higher incidence of extra-larval moults than in control animals receiving unchilled brains. The ability of the implanted brains to induce an extra-larval moult depends on the number of implanted brains, age of larvae at chilling and the time interval between cooling and removal of the brain. The implanted brains must be present in the host larva for at least 2 days in order to induce an extra-larval moult. The brain taken from a chilled larva has no effect on the activity of the host brain. Application of fluoromevalonate (FMev) to insects which received the brains taken from chilled larvae suppresses the extra-larval moult responses, while implantation of brains from chilled larvae treated with FMev has no effect on the incidence of extra-larval moults produced by the recipients. The possibility that the chilled brain of Galleria larvae produces a hormonal factor that regulates corpora allata activity (allatotropin) is discussed.