The hourly feeding activity rhythm of A. imperator has been studied. The larvae were placed in individual dishes with 10 standard sized chironomid larvae each: eaten prey were replaced every hour. In the laboratory, under natural lighting, the number of hourly captures, the number of larvae having eaten, and the number of prey captured per larva, all reached a first maximum in the evening at dusk, and a second maximum early morning, at dawn. Data from observations in February, June and October were qualitatively comparable but differed quantitatively. Excretion does not seem to be influenced by nycthemeral variations. Variations of light intensity seem to influence the nycthemeral distribution of feeding activity of larvae provided with plenty of prey; in continuous light no significant variations of feeding activity could be observed.