Abstract
A feeding actograph consisting of an activity detector, an amplifier, a pen-recorder and a timer circuit was designed to determine the daily change in feeding activity in the silkworm Bomcbyx mori L. Masticatory motions were detected by the changes in electrical resistance between an electrode implanted in the haemocoel of the thorax and the second electrode attached to the artificial diet. The main circuit of the amplifier was made up with a simple magnifier and a voltage comparator. A voltage comparator effectively functioned to eliminate noises. To get the signals driving the timer circuit, an integrating circuit was provided. The timer circuit includes an electronic relay, a clock pulse (1 Hz) generator, a pulse counter and a digital printer. By use of this instrument, the feeding rhythms in the 5th instar larvae of the silkworm were analused in several lighting resumes such as 8L-16D, 12L-12D, 16L-8D and 20L-4D. In the long-day condition of 20L-4D, the activity value of feeding—total duration of active feeding (min) measured in 2-hour intervals—fluctuated in monophasic pattern with a peak at the middle part of photophase, while in the short-day conditions below 16L-8D, the value fluctuated in bimodal pattern with the 1st peak at the middle of photophase and the 2nd peak at 7th-8th hour period of darkphase. These facts seems to suggest that the timing of silkworm feeding was adjusted by both of the diurnal type rhythm mechanism and the nocternal type rhythm mechanism.
