Abstract Specific cycles in oxygen consumption occur in each instar of Galleria. Three types of cycles have been recognized: the first appears in the penultimate larval instar, the second in the last larval instar, and the third in the pupal instar. When the brain-corpora cardiaca-corpora allata complexes were implanted into freshly moulted last-instar larvae, metamorphosis was delayed, and two to five extra larval instars were induced. Such artificial giant larvae developed finally into giant pupae and these formed morphologically perfect giant moths. The extra larval instars retain the first type of oxygen consumption cycle, the last extra larval instars keep the second type, and the giant pupae retain the third type. Thus it follows that both the larval development controlled by the corpus allatum hormone and the metamorphosis proceeding in its absence are distinguished by specific changes in overall metabolism, regardless of the absolute age and size of the specimen. Changes in metabolic activity induced by hormones were found to be closely correlated with the degree of morphogenetic change. It is concluded that the corpus allatum hormone has an indirect effect on metabolism.