Scientists test freezing butterfly eggs to save the endangered British Swallowtail.

Researchers at Anglia Ruskin University are testing cryopreservation—freezing butterfly eggs in liquid nitrogen at -196°C—to help conserve the rare British Swallowtail, which has declined by 57% over the past two decades due to habitat loss, climate change, and low genetic diversity. Using eggs from a closely related, more abundant species at Jimmy’s Farm and Wildlife Park, scientists aim to determine if frozen eggs can develop into healthy, reproductive butterflies. If successful, the method could enable long-term storage of genetic material for future breeding and reintroduction efforts. The project, supported by UK biobank Nature’s SAFE, is believed to be the first of its kind for butterflies and could benefit other pollinators and invertebrates, supporting broader conservation and ecosystem health.