The swallowtail butterfly has exceptionally large wings relative to its body mass, a feature that makes its in-flight movements unique.

This scale model, which copies the shape of the swallowtail's wings and the thin veins and membranes that cover them, reveals that the insect achieves forward motion with simple flapping movements. Other butterflies have different flight characteristics.

The mechanical butterfly was built by Hiroto Tanaka and Isao Shimoyama at the University of Tokyo and is reported in the journal Bioinspiration and Biomimetics.