[A study of the structure and activity of the endocrine organs in Cerura vinula L. (Lepidoptera) during the pupation]

Abstract

The neurosecretory cells of the brain, the prothoracic gland, and the corpora allata ofCerura vinula L. undergo phases of secretory activity in every larval instar. In the last (fifth) instar, the activity of the corpora allata is only weak. The neurosecretory cells of the brain are active from the 3rd day of the fifth instar till after pupation. The activity of the prothoracic gland lasts from the 3rd day of the fifth instar to the beginning of the moulting process in the integument, about 6 days after spinning. It has a small maximum of activity about 1 day before the larva turns red and begins to spin its cocoon; and a second one after the red epidermal pigment has vanished, i.e. before pupal moult sets in. These morphological results are in accordance with the assumption that all of the processes involved in pupation are brought about by the prothoracic gland hormone ecdysone. Haemocytes have been found among the cells of the prothoracic gland during its period of activity. In the pupa and the adult moth the corpora allata undergo periods of secretory activity, the function of which is not yet clearly understood. The thorax of the larva contains an additional endocrine gland, extending through the dorsal fatbody, the function of which is still unknown.