On the relation between pigment position and light sensitivity of the compound eye in different nocturnal insects

Abstract

In contrast to the rapid smooth dark-adaptation curve of day-flying insects lacking migratory secondary iris pigment, the adaptation curve of nocturnal moths and other night-flying insects, equipped with migratory secondary iris pigment, has in principle a diphasic course. During the second phase the eyes of the latter group acquire a considerably higher sensitivity than the dark-adapted eyes of the insects lacking secondary iris pigment. In comparative electrophysiological and histological investigations further evidence is presented for the conclusion that the second phase of the dark-adaptation curve is due to the migration of the secondary iris pigment from dark position to light position. The prerequisites for the appearance of the pigment migration and the second phase of the dark-adaptation discussed. The variations in latency and temporal course of the curve are second phase in the same species, and in different species, are discussed and attributed to variations in the time course of the secondary iris pigment migration.