CIRCADIAN-RHYTHMS IN THE SOCIABILITY AND LOCOMOTOR ACTIVITIES OF THE MILLIPEDE, JONESPELTIS-SPLENDIDUS VERHOEFF

The circadian rhythm of the locomotor activity of the millipede Jonespeltis splendidus Verhoeff was studied under three different regimes. 12 L:12 D condition resulted in the establishment of persistent bimodal crawling activity at twilight (18:00 hr) and before dawn (6:00 hr). A lull in the activity (aggregation) occurred at night between 21:00 to 2:00 hr: and during the day between 11:00 to 15:00 hr. The total light caused the peaks of activity rhythm to shift erratically. The total darkness condition altered the rhythm drastically. The sociability (aggregation) behavior, as indicated by the sociability index, is paired with a slow locomotory rate, while low sociability corresponds to a high activity rate. The aggregations in the millipedes were induced more by the darkness factor than by the condition of soil. An assay of secretions responsible for aggregations showed the occurrence of volatile agents which are secreted rhythmically by the abdominal glands. These secretions are believed to initiate responses for aggregations. © 1979 Academic Press, Inc.