Background
Diversity and distribution of Neotropical aquatic insects is still poorly known, with many species to be recorded and many others to be described, due to the small number of taxonomists and sparse faunistic studies. This knowledge is especially poor in the Caatinga Domain in Northeastern Brazil, even though, this region may have played an important historical role in the spatial evolution of faunas of forested areas in northern South America. New information: Aquatic insect checklists of 96 species from Parque Nacional de Ubajara (Ceará State, Brazil) and 112 species from Parque Nacional de Sete Cidades (Piauí State, Brazil) are presented, representing the following taxa: Elmidae, Epimetopidae, Hydrophilidae, and Torridincolidae (Coleoptera), Hemerodromiinae (Diptera: Empididae), Ephemeroptera, Gerromorpha and Nepomorpha (Hemiptera), Odonata, Plecoptera, and Trichoptera. Because of the scarce number of biological inventories in Northeastern Brazil, several new distributional records (of species, genera, and families) for Brazil, Northeastern Brazil, and Ceará and Piauí states are provided. In addition, several undescribed species were detected, being 26 from Ubajara and 20 from Sete Cidades.