[Changes of oenocytes and their function during metamorphosis of sphingidae and notodontidae]

Oenocytes of the last larval instar and the pupa ofCerura vinula andSpinx ligustri have been examined, and their structure described. The activity phases of the oenocytes at the time of both moultings, as well as during the last larval instar prior to an externally visible color change and prior to the pupal ecdysis i.e. during color change stage III) were clearly related to the process of metamorphosis, which was occurring in the larvae at this time 2-4 months after pupal ecdysis, diapausing pupae still show active larval oenocytes. Activity phases are characterized by many large and small vacuoles in addition to channel-like cytoplasmatic structures, heavily branched nuclei and extensive cell processes and infoldings of the cell membrane. In the pharate pupal stage (colour change stage IV) the imaginal oenocytes originate from the hypodermis, becoming active just prior to the adult ecdysis.Haemocytes containing neurosecretory material attach themselves to the oenocytes and enter through infoldings of the cell membrane. Lipids, which are particularly abundant during active phases, could be demonstrated in the cytoplasm as well as passing from the fatty tissue closely surrounding the glands. Glycogen was also present in the oenocytes. There was, however, no noticeable relation of these materials to the rhythm.Physiological experiments demonstrated that oenocytes as well as prothoracic glands, when active, secrete the moulting and metamorphosis hormone. Both glands initiate the process of colour change. Brain tissue, containing active neurosecretory cells, or cholesterol, may stimulate the prothoracic galnds and the oenocytes to secrete their hormone.