Mexican jumping beans are not beans but actually caterpillars. They are Cydia deshaisiana moth caterpillars maturing in the fallen seedpods of Sebastiania shrubs, which thrive in the hot, dry Mexican climate.
Why do Mexican jumping beans jump?
The adult moth lays its egg on a developing pod, and the hatched larva nibbles its way inside. The youngster reacts to light and heat, violently jerking its body in an attempt to seek shade, causing the seed to jump.
It only stops moving when it is out of the sun’s dangerous, drying glare. After the pupal stage, the silver-grey adult moth eats its way out of the seedpod, and the cycle starts again.
Main image © I, NobbiP, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
