Predator efficacy and attraction to herbivore-induced volatiles determine selection of a nutritionally inferior host plant in a moth
Unlike mammals, most invertebrates provide no direct parental care for their progeny, except a limited amount of yolk and a well-selected oviposition site. However, little is understood of how gravid females evaluate opportunities and threats when choosing an oviposition site. Leveraging the wide range of host plant use in a polyphagous pest, Spodoptera littoralis , we investigate oviposition choice and predator activity between two host plants of different nutritional quality. Oviposition experiments and field surveys reveal that females preferred to lay eggs on a host plant, which exhibit an inferior nutritional quality and harbor more natural enemies. However, we found that predation rates of S. littoralis larva and pupae were lower on this plant. Through investigating the predator search and olfactory-guided behaviors, we show that a major predator is more successful in finding S. littoralis and more attracted to herbivore-induced olfactory cues from the superior host plant. Our results show that enemy free-space between host plants is dependent on predator efficacy and odor-gui ded attraction, but not predator abundance, and could contribute to the weak correlation between preference and performance during host plant choice in S. littoralis and in insects in general.