Mexican Jumping Beans are small, brown beans which appear to jump, hop, and move about when stimulated by heat or light. This BBC show explores their strange nature, and reveals what makes them dance.
The Mexican Jumping Bean is actually the seed of a shrub native to Mexico. What makes it move around is the presence inside of a caterpillar which, if left to grow fully, turns into a Jumping Bean Moth.
A caterpillar inhabits the seed because an egg is laid inside it. The caterpillar then eats the inside of the seed in order to grow, making more room for itself as it does so. The movement comes from the caterpillar seeking shelter from the Mexican sun.
This video shows how sensitive the caterpillars are to heat and light, with the Mexican Jumping Beans seeking shade at the first available opportunity. Which is pretty damn awesome. The only disappointing factoid is that the moths only live for a few days after they hatch.
