Altered host plant volatiles are proxies for sex pheromones in the gall wasp Antistrophus rufus.

We describe a previously uncharacterized function for changes in plant chemistry induced by phytophagous insects: to provide cues for mate location. Larvae of the gall wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae) feed within inconspicuous galls inside the flowering stems of the prairie perennials Silphium laciniatum L. and Silphium terebinthinaceum Jacquin (Asteraceae).