 DNA methylation is an important gene regulatory mechanism in mammals, but its function in arthropods has been poorly understood. In new social insects, it has been suggested that DNA methylation may play a role in cast development by regulating gene expression and splicing. However, these findings have been inconsistent, leading to controversy over its role in this process. To investigate further, researchers use CISPR-Cas9 to mutate the maintenance DNA methyl transferase DNA-MT1 in the clonal radar ant, Osaria beroi. The mutant ants had significantly reduced levels of DNA methylation, but no observable developmental defects. Furthermore, there was no evidence that DNA methylation played a role in cast development. Instead, the mutated ants were sterile, suggesting that DNA-MT1 plays a critical but as yet unidentified role in the insect germline. This article was authored by Irina Ivasek, Leonora Oliva Cisneros, Stephanie Valdez Rodriguez, and others.