text: In positive plant-insect interactions, GLVs are used as a form of defense. They attract predators to plants that are being preyed upon by herbivores. 
  For example, female parasitoid wasps from two different families, Microplitis croceipes and Netelia heroica, can be attracted to plants that are emitting GLVs due to wounding from caterpillars. Maize plants emit volatiles to attract the parasitic wasps Cotesia marginiventris and Microplitis rufiventris to attack African cotton leafworm. In some species GLVs enhance the attraction of sex pheromones. For example, green leaf volatiles have been found to increase the response of tobacco budworm to sex pheromone. Budworm larvae feed on tobacco, cotton, and various flowers and weeds, and in turn can be fed on by the larvae of cohabiting species that are attracted by GLVs.
  In another study, a multi-plant relationship was reported. The parasitic wasps (Vespula germanica and V. vulgaris) prey on caterpillar (Pieris brassicae)-infested cabbage leaves that emit GLVs.  The same GLVs are emitted by the orchids (Epipactis purpurata and E. helleborine) through pheromone release. The orchids benefit from attracting the wasps, not to protect them from insects, but because the wasps aid in pollination.
  Benefits of GLV release have also been reported in soybeans grown in Iowa. When these soybean plants became heavily infested by aphids, the amount of GLV released far surpassed normal levels and as a result, more spotted lady beetles were attracted to the pheromone releasing plants and preyed on the bugs eating the plant. The stimulus of aphid predation is chemically transmitted through the plant to coordinate an increase release of GLV’s. The particular chemical released is unique to these spotted lady beetles and when different species of beetles were tested, there wasn’t any extra inclination for them to move towards GLV releasing plants. This indicates that these soybeans evolved ability to release species-specific pheromones to aid in their survival.