Do host plant volatiles influence the diel periodicity of caterpillar foraging of all species attacking the same host plant

Abstract

Shiojiri et al. reported that host plant (corn) volatiles rather than photoperiod influenced the diel periodicity of larvae foraging behavior in Mythimna separata. We undertook experiments to determine if the same trends were observed in two other noctuid species, M. unipuncta and Spodoptera litura, that also use corn as a host. In the case of Mythimna separata we again observed a significant direct effect of host plant volatiles and not light conditions. However, the inverse was true for the other two species, although the host plant effect approached significance for M. unipuncta. In all three species there was a significant Light X Plant interaction. The observed differences could reflect interspecific differences in life history traits such as diet breadth and voltinism. However, all species tested had been in rearing on an artificial diet for a number of generations and inadvertent selection may have influenced the behavior under consideration. To eliminate this possibility, additional experiments need to be conducted, using newly established colonies.