Olfactory response of the omnivorous mirid bug Nesidiocoris tenuis to eggplants infested by prey: Specificity in prey developmental stages and prey species

Abstract

We studied olfactory responses of Nesidiocoris tenuis Reuter (Heteroptera: Miridae), an omnivorous mirid bug, to volatiles from eggplants infested by different developmental stages of tobacco cutworms, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) and of female two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae). We first conducted predation experiments and found that N. tenuis preyed on first and second stadium larvae, but not on third and fourth stadium S. litura larvae. N. tenuis also preyed upon T. urticae females that had been reported to be less suitable prey species. When offered first stadium S. litura larvae and T. urticae females simultaneously, N. tenuis, preferred to prey upon S. litura larvae. We then tested the olfactory responses of N. tenuis to volatiles from eggplants using a Y-tube olfactometer. A significant preference for volatiles from uninfested eggplants over clean air was found. Volatiles of eggplants infested by either first, second or fourth stadium S. litura larvae were preferred over volatiles from uninfested eggplants. The olfactory preferences of N. tenuis to S. litura-infested eggplants were: eggplants infested by 10 first stadium larvae=eggplants infested by 10second stadium larvae>eggplants infested by 1 fourth stadium larva. Volatiles from eggplants infested by 200 T. urticae females also attracted N. tenuis, but the volatiles were not as attractive as those from eggplants infested by 10 first stadium larvae. Chemical analyses showed that volatiles from eggplants infested by different developmental stages of S. litura larvae had qualitative differences. First stadium larvae induced higher amounts of volatiles than second and fourth stadium larvae, despite the first stadium S. litura larvae doing the least damage. T. urticae female-induced volatiles were both qualitatively and quantitatively different from those induced by first stadium S. litura larvae. The specific olfactory responses of N. tenuis to different prey species/developmental stages were discussed in terms of prey availability and biological control.