A Study of spontaneous Locomotor Activity inLocusta migratoria migratorioides(R. & F.) by the Actograph Method

Abstract

An actograph apparatus is described for recording in 24-hour periods, under controlled conditions, the activity ofLocusta migratoria migratorioides(R. & F.) in terms of distance travelled.Great variation was observed in the amount of activity shown by different individuals and the activity of any one individual is shown to vary considerably over each stadium, the highest level occurring about half-way between moults, and falling off towards the beginning and end of each stadium.An insect is shown to be capable of very intense activity immediately before a moult if no convenient moulting place is found.No significant difference is found between the activity of males and females, but the average distance travelled in a 24-hour period in the 4th and 5th stadia is shown to be greater than that in the 2nd or 3rd.The daily activity of adults is shown to vary considerably from day to day, and the diurnal distribution of the activity of adults up to seven days old is shown to be similar to that of nymphs.The unequal distribution of activity over each 24-hour period is shown to be due to absence of fresh food in the second half of each record, and the effect of this starvation is shown to vary according to the stage of development of the insect.The effects of changes in relative humidity on the amount and distribution of activity are shown to be very slight or none.A diurnal periodicity is shown to be induced in the insects when reared under alternating 12-hour periods of light and dark. The longer the conditioning lasts, the more clear-cut is the periodicity. In constant darkness the periodicity is retained for only a few days and gradually disappears.A tendency for periods of high activity to recur every 2–2½ hours is demonstrated in certain records. In the other records, constituting actually the majority, it is suggested that the periodicity is masked or that the locust's nervous mechanism is inadequate to maintain it.Preliminary experiments with a form of trophograph suggest that the 2–2½ hour periodicity may be associated with a hunger rhythm.