Corpora allata of honeybee worker larvae 48 h of age are capable of activating Periplaneta female accessory glands. Corpora allata from queen larvae of the same age are repressive in action. By 72 h of age the worker allata have a considerably reduced activity but queen larvae of the same age have allata of the activating type. Thus, corpora allata show a duality in function during caste development.