Abstract
Behavioural evidence is presented for the presence of an oscillation underlying feeding and a number of other activities in fifth‐instar Locusta migratoria nymphs raised and observed under LD 12:12 with constant access to food. With the oscillation represented for convenience as a sine wave, these behaviours occurred significantly more often in the peak half of the cycle than in the trough half. The period of the oscillation differed between insects, the range being from 12.0 to 16.5 min, but was constant for each insect. Feeding did not occur on every cycle but when it did occur it usually began near the peak of an oscillation. Off‐peak feeding was generally associated with defecation. Other more frequently exhibited behaviours, such as the initiation of locomotion and a variety on non‐locomotory behaviours, occurred on peaks when there was no feeding. Once feeding or locomotion had commenced and during the short period of settling afterwards, rhythmicity in the non‐locomotory behaviour was lost. The nature of the oscillator is not known, other than it is apparently endogenous and is not reset during a 12‐h light phase. The presence of such an intermediate length oscillator may have important implications in the organization of complex behaviour