The karyotypes and course of meiosis of two pseudoscorpions, Semeiochernes armiger (Balzan 1892) and Cordylochernes scorpioides (Linnaeus 1758) (Pseudoscorpiones: Chernetidae), are described for the first time. The diploid chromosome number of the male is 69 in S. armiger and 47 in C. scorpioides. As in most pseudoscorpions studied to date, autosomes exhibit predominantly biarmed morphology. Both species possess an X0 sex chromosome system. In most pseudoscorpions with X0 system karyotyped so far, including European chernetids, the X chromosome exhibits metacentric morphology. In contrast, the X chromosome of both neotropical chernetids studied exhibits asymmetric, submetacentric morphology.