Experimental evidence that plants under caterpillar attack may benefit from attracting parasitoids

Herbivore-induced plant volatiles have been suggested to function as indire ct defence signals that attract natural enemies of herbivores. Several inse ct parasitoids are known to exploit such plant-provided cues to locate host s. It is unclear if individual plants benefit from the action of parasitoid s. We investigated this question in maize plants under attack by Spodoptera littoralis larvae and found that parasitization by the endoparasitoids Cot esia marginiventris and Campoletis sonorensis significantly reduced feeding and weight gain in the host larvae. As a result, young maize plants attack ed by a single parasitized larva suffered much less feeding damage and, at maturity, produced about 30% more seed than plants that were attacked by an unparasitized larva. Such fitness benefits may have contributed to selecti on pressures that shaped the evolution of herbivore-induced indirect defenc e signals in plants.