Mexican jumping beans (also known as frijoles saltarines in Spanish) are not actually beans. They are brownish seed pods of a Mexican shrub called Sebastiania pavoniana that have been implanted with larva from the Laspeyresia saltitans moth. The larva inside the pod eats the seed leaving a lot of empty space in it. Once the seed is gone, this larva has room to leap around, causing the “bean” to move and roll around. They tend to move more the hotter it gets in an attempt to get to a cooler environment to avoid dehydration which is deadly. The larva even creates a complex network of silk lining inside the pod to give it more jumping energy, which results in allowing it to “jump” further.
- Under the right conditions, the larvae will live for months.
- If the larvae survive until spring, it will eventually become a moth and exit the pod through a trap door.