Abstract The ant genus Pheidole is the most species-rich lineage of ants in the world and one of the dominant organisms in tropical regions. However, the knowledge of Pheidole diversity in the southern half of the Neotropical Region is fragmentary. Here, we offer contributions to the Pheidole taxonomy considering the species that occur in the grassland formations of South Brazil. The following species are revived from synonymy: P. idiota Santschi rev. stat., P. obscurior Forel rev. stat., P. paranana Santschi stat. rev. et n. stat. and P. strobeli Emery rev. stat. The following synonyms are proposed: P. idiota (= P. laticornis Wilson n. syn.), P. obscurior (= P. partita Mayr n. syn., = P. incisa evoluta Borgmeier n. syn.) and P. strobeli (= P. rufipilis divexa Forel n. syn., = P. nitidula daguerrei Santschi n. syn., = P. perversa Forel n. syn., = P. perversa richteri Forel n. syn., = P. strobeli misera Santschi n. syn.). Finally, six new species are described: P. abakytan n. sp., P. abaticanga n. sp., P. cangussu n. sp., P. curupira n. sp., P. mapinguari n. sp., and P. obapara n. sp.

Abstract The state of Maranhão, located in northeastern Brazil, comprises three biomes: Amazonian, Caatinga, and the Cerrado. To date, 99 ant species have been recorded in the literature from the state. In the present work, we provide for the first time a profile of the ant fauna in the state based on data from the historical literature and Brazilian institutional collections. The updated records on ant diversity for the state of Maranhão revealed a total of 279 species, belonging to 71 genera and 10 subfamilies. In total, 180 species are recorded for the first time in the state, of which four species recorded for the first time in Brazil. In summary, apart from documenting the ant fauna of the region, these results provide a basis for further studies and may contribute to future conservation efforts for the biomes present in this complex landscape.