Interactions between zoophytophagous heteropterans and their host plant

Several economically important biological control agents, among which the mirid N. tenuis and the anthocorid O. laevigatus, are predators that maintain a close relationship with their host plant. Not only do they deposit their eggs in plant tissues, they also display a feeding habit called zoophytophagy. This dissertation focuses on this complex relation and tries to give an answer to two research questions: (1) what nutrients are obtained from plants during embryogenesis or by plant feeding and (2) which biochemical reactions take place in plants upon infestation with these bugs. Our experiments suggest that water acquisition is the primary function of plants for N. tenuis and O. laevigatus. However, supplementary nutrients derived from plants may enhance survival in the absence of prey and have a positive effect on the weight of adults. Knowing the role of plants for both N. tenuis and O. laevigatus, we were able to rear those predators on lab scale in the absence of plants for several generations without major fitness loss. In the second part of this thesis, we showed that both predators activate a JA-mediated wound response in their host plant. As a result of the induced defense, plants inhabited by O. laevigatus appeared more resistant to thrips feeding compared to control plants. Additionally, we demonstrated that the mirid predator N. tenuis induces the emission of volatile compounds, such as p-cymene, which has been reported to have a repellent or toxic effect on herbivores. Based on these results, we hypothesize that zoophytophagous heteropterans not only exert a direct effect on herbivores by preying on them, but also an indirect effect by activating a JA-mediated wound response