A long series of parthenogenetic generations, as present in at least four of the studied species, could lead to an accumulation of genetic abnormalities, including chromosome mutations. Considering this, the variations in chromosome numbers observed for S. sipylus and P. khaoyaiensis may be due to laboratory linages with such chromosomic features or to technical problems. Indeed, embryos were used to obtain chromosomes, thus, selected eggs may have genomic imbalances, which would have been lethal in the egg or shortly after hatching. Thus, the questions of chromosome number variation and the probable structural rearrangement in polyploid species of stick insects in culture remain open for the moment.