In conclusion, our results indicate that, in contrast to theory and evidence from other taxa, worker bumblebees retain the queen-like abilities to mate and found successful colonies. This suggests both that there is active selection to retain these traits, as opposed to selection in other eusocial taxa that has degraded them in workers, and that the evolution of eusociality is potentially a reversible step. While the importance of this worker reproduction under natural conditions remains to be determined, its discovery provides a new tool to combat global declines in bumblebees. Artifical insemination of workers from rare and declining species could be used to generate large numbers of gynes for release back into the wild, reinforcing and reintroducing bumblebees to habitats where they are essential pollinators.