A mink skull tries to catch a butterfly every time that it come closer to its mouth, but it never succeeds.

A butterfly fixed on the free point of an inverse Peaucellier-Lipkin linkage describe a cardioid trajectory around the main axle of the Mecanotrope above which a mink skull is mounted.

This kind of linkage lets the butterfly go further the mink when it is behind it and come closer when it passes in front of mink’s mouth. One of the links gives motion to a pinion that carries a small piece that acts  mandible’s levers for a small fraction of the cycle. Mink’s mouth opens when the butterfly passes in front of it and it fast closes once it is passed by. A small movement of the skull go with the mandible’s one.