The control of spittlebugs, in general, is compromised by the failure to recognize that the impact of this insect pest can vary greatly, due to taxonomic diversity, the extent of habitats, climatic factors and pasture management. Furthermore, insects and plants co-evolve and this factor must be taken into account, since the discovery of resistant cultivars requires a relatively long period and the knowledge of the bases of the insect-pest interaction with the plant can be a key point for the reestablishment of the favorable factor for the plant. This scenario points to the need for basic studies aiming at a closer knowledge of the genetic and chemical bases involved in the insect “versus” plant interaction. Thus, the objective was to evaluate the interaction of the spittlebugs with the forages of the genera Brachiaria and Pennisetum in molecular and biochemical bases. Research concerning the identification of the genetic variability of spittlebug specimens, based on RAPD (random ampliified polymorphic DNA) molecular markers was conducted; the electrophoretic protein profile of spittlebug foams was evaluated; phenols produced by the plants were evaluated as indicators of resistance to spittlebugs through the use of nitric oxide, as well as the study of resistance to grasshoppers in Brachiaria clones. In the first research action it was found that there is high genetic variability of the specimens of Mahanarva spectabilis and that the cluster analysis separated the species M. fimbriolata, M. spectabilis and M. liturata. Six unique markers were identified, present in all M. spectabilis individuals and, similarly, eight unique markers for M. fimbriolata and four for M. liturata. These markers can be used to help identify these species, since the external morphological characteristics commonly used by taxonomists are difficult to assess, mainly due to the variation in the tegmina pattern. As for the protein content of the foams from different genetic materials of elephant grass and brachiaria, the interaction of protein expression of different molecular weights with the different plant genotypes offered to the spittlebugs was evidenced; in the same way it was possible to make an association between the protein expressions with the resistant and susceptible control plant materials. In the study of resistance induction, it was found that the application of nitric oxide increased the polyphenol content of elephant grass plants, being promising to increase the resistance of this species to the attack of M. spectabilis. It was also verified a great genetic variability of the clones of B. ruziziensis for the resistance to spittlebugs. However, it was not possible to relate plant molecular-based genetic differences with resistance or susceptibility to spittlebugs by the antibiosis test. Thus, it was possible to identify factors that involve the specificity between the studied forage species and spittlebugs, in order to expand the alternatives for controlling this pest.