none. Insect-plant relationships not only include interactions between plants and herbivores or pollinators, but also with a third trophic level, parasites, parasitoids and predators of plant herbivores. Plants may manipulate the different trophic levels in many ways, but the role of volatile allelochemicals in attracting or repelling herbivores and parasitoids, and the effect of toxic allelochemicals on herbivores, both directly and acting through the herbivore on parasitoids, are of particular interest. These studies utilized cotton, Gossypium hirsutum as the plant; the tobacco budworm, Heliothis virescens , as the herbivore; and the ichneumonid, Campoletis sonorensis , as the parasitoid. Using a Petri dish bioassay, a "Y"-tube olfactometer, and a filtered air flight chamber olfactometer, the authors examined the role of plant volatiles influencing the behavior of C. sonorensis .