The goal of the dissertation is taxonomic and trophic assessment of the Nepticuloidea fauna (Lepidoptera: Nepticulidae, Opostegidae) of Middle and South America in the light of the latest taxonomic and trophic data. The dissertation consists of Introduction, Literature Review, Material and Methods, Results of the Research, Summary, Conclusions, References, List of Publications by the Author (57 sources) and Annex (Preliminary Catalogue of the studied fauna). The dissertation deals with comprehensive taxonomic analysis of the Nepticulidae and Opostegidae of Middle and South America which allowed to designate many new species groups and to provide diagnostic pictorial keys. The dissertation also deals with newly discovered ecological adaptations and with the first trophic analysis of the Nepticulidae from the Neotropical and Ando-Patagonian regions, where the predominating trophic associations with Asteridae and Rosidae were revealed and trophic relationships with 24 families and 16 plant clades were recorded. In total, we identified new host-plant data for 114 Nepticulidae taxa (including undescribed species), i.e. the number of newly revealed trophic relationships of Nepticulidae of the region under research amounts to almost 86%. We also discovered 146 previously unknown (new) species, most of them were published