Programmed cell death in the nervous system of an adult insect.

The tobacco hornworm moth, Manduca sexta, shows extensive degeneration of abdominal neurons after the adult moth emerges (ecloses) from the old pupal skin. Death of interneurons begins about 2 hours before eclosion and continues through the next 30 hours. Motorneuron degeneration starts slightly later, commencing at about 8 hours after eclosion. Analysis of the death of identified motorneuons showed that there was a precise spatial and temporal program of neuronal death. Particular cells invariably either continued to live or died and, among the latter, the time of death varied from cell to cell but for a given cell was constant. This program of cell death was somewhat flexible in that the fates of certain cells could be adaptively modified by behaviors that might naturally occur in the life of the insect.