ABSTRACT
The karyotypes of Neotropical Pseudomyrmecinae were analyzed for the first time. Seven species belongingto the Pseudomyrmex genus from four Brazilian localities had their chromosome number and morphologystudied. Six of the nine species groups of Pseudomyrmex were sampled. Chromosome numbers rangedfrom 2n=24 to 2n=70, characterized in acrocentrics and metacentrics. Our cytogenetic studies indicatethat, as in other ants, karyoptype evolution in Pseudomyrmex may have evolved increasing chromosomenumber and diversifying chromosome morphology, minimizing genetics risks for deleterious mutationsthrough centric fission and pericentric inversion. Such a karyotypic diversity is also recognized in otherants subfamilies, especially Myrmeciinae, Ponerinae and Myrmicinae. These first cytogenetic studies in thegenus Pseudomyrmex should contribute with other data to the evolutionary history of the Pseudomyrmecinaesubfamily.