Circadian activity rhythms of Ephestia cautella in response to predation risk by natural parasitoid Habrobracon hebetor

Almost all organisms have evolved their own internal biological clocks which affects almost all behaviors. These clocks are synchronized to the 24 h light/dark cycle by external environmental cues, so-called Zeitgebers, such as light and temperature. This enables them to anticipate and prepare for predicted changes in the timing of the species they interact with. Several studies have well-characterized the circadian activity of lepidopteran adults but much less is known about daily activity in the larval stage, especially in the presence of its natural parasitoid wasp. Our research aims to study the circadian activity rhythms, mainly locomotion of larvae of Ephestia cautella which is a lepidopteran pest. The activities were recorded in the presence and absence of its natural parasitoid wasp Habrobracon hebetor. The results showed rhythmic behavior in both the presence and absence of the parasitoid but with a phase shift in time of activity. Intriguingly, the shift of activity in the presence of parasitoid leads to synchronized activity of moths` larvae. In the presence of the wasp, the larvae movement characteristics suggested a fleeing behavior, i.e., straight and quick walk. Thus, the results suggest that in these species, avoidance of enemy by temporal niche separation is not beneficial but rather a runaway strategy. This is the first study to show evidence of a temporal shift in time of activity of the host species.