DNA replication in the spermatogonial cells of Schistocerca gregaria and Gryllotalpa fossor has been analysed. This study has demonstrated the presence of at least two discrete populations of spermatogonial cells in both the insects with different intermitotic timings. The replication pattern of the sex chromosome in Schistocerca seems to be dependent on the pycnosity status, whereas, in Gryllotalpa, it is independent of the condensation pattern.