The main purpose is the understanding of the influence of plant characteristics on growth, distribution and genetic diversity of insect populations. The impact of the host plant (maize) on the genetical polymorphism of aphids is quantified using PCR techniques. Similarly, the concentration of resistance factors in the plant, such as hydroxyamic acid and related compounds, are determined and followed through time. The other groups studied are thrips, whiteflies and mites in glasshouses, and mites in maize and sugarbeet crops. Furthermore, research is carried out on the characterisation of endosynbionts of the genus Buchnera and on their role in aphid host-plant adaptation.