Abstract
The systematic of the family Phytoseiidae is not presently based on solid phylogenetic studies and therefore, many taxonomic questions still arise, concerning the validity of supra-specific and specific taxa identified to-date. This thesis thus aimed to answer such questions for two genera, Phytoseiulus and Neoseiulella, using for the first time molecular and morphological phylogenetic analyses. Biogeographic analyses have been also carried out. Results obtained by both morphological and molecular approaches are congruent and seem to show that both genera are not monophyletic: Phytoseiulus seems paraphyletic whereas Neoseiulella seems polyphyletic. These results are different from those encountered in previous revisions of these two taxa. Furthermore, this study allowed to conclude on five synonymies within the genus Neoseiulella. The observation of nearly the totality of the type materials of the genus Neoseiulella permitted to redefine this genus, excluding three species and discussing some synonymies. Lastly, an identification key to the valid species of the genus Neoseiulella based on adults females was proposed. Further experiments, including molecular investigations, are however still required in order to obtain more reliable conclusions on the evolutionary relationships of the studied taxa.