Parasitic wasps existed as early as several million years ago. Within a project coordinated by Karlsruhe Institute of Technology (KIT), researchers of various disciplines for the first time definitively discovered fossil parasites inside their hosts. The scientists studied fly pupae from old collections using ultrafast X-ray imaging. They found 55 cases of parasitation and described four extinct wasp species that were unknown until now. The project was managed by the KIT. Researchers from HITS and Heidelberg University developed the algorithms and software for the digital reconstruction. Their findings are reported in Nature Communications.