Insects and their hostplants are thought to be in an evolutionary arms race, but a great difficulty of studying insect-plant interactions is to establish what exactly an insect feeds on. We demonstrate a remarkable preservation of hostplant DNA within the insect that leaves a permanent record of the food source. Plant DNA was readily obtained from DNA extractions of herbivorous insects and identified against existing sequence databases, for an unequivocal identity of the foodplant.

When applied to poorly known leaf beetles of Australia, evolutionary lineages were conservative in their host use, but also underwent some dramatic shifts to unrelated hostplants.

Proceedings of the Royal Society B: Biological Sciences

Proceedings B is the Royal Society's flagship biological research journal, dedicated to the rapid publication and broad dissemination of high-quality research papers, reviews and comment and reply papers. The scope of journal is diverse and is especially strong in organismal biology.

Proceedings of the Royal Society B: Biological Sciences