Why does a mexican jumping bean jump?
Mexican jumping beans are a phenomenon native to Mexico where they are known as brincadores. Physically, they resemble small tan or brown beans. They are a type of seed in which the egg of a small moth has been laid. It is the moth’s larva which makes them ‘jump’. The beans themselves are from a shrub of the genus Sebastiania (S. palmeri or S. pavoniana), while the moth is of the species Cydia deshaisiana. After the egg has hatched, the larva eats away the inside of the bean, making a hollow for itself. It attaches itself to the bean with many silken threads. When the bean is abruptly warmed, for instance by being held in the palm of the hand, the larva twitches and spasms, pulling on the threads and causing the characteristic hop. “Jump” is often an exaggeration, but the beans are nonetheless far from immobile.
