Mexican jumping bean
From Wikipedia, the free encyclopedia
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.
The larva may live for months inside the bean with varying periods of dormancy. If the larva has adequate conditions such as moisture, it will live long enough to go into a pupal stage. Normally in the spring, the moth will force its way out of the bean through a round "trap door", leaving behind the pupal casing.
The small, silver and gray-colored moth will live for only a few days.
Jumping beans were used as a recurring gag in many cartoons in the 1930s to the 1950s. They are particularly common in the northern desert states of Sonora and Chihuahua; indeed, Álamos, Sonora, claims to be "the jumping bean capital of the world".
They are still widely available for sale in the USA, being very close to the native Mexico habitats. In the UK they were a common novelty item in the 1970's. They are a popular scientific/classroom project even now.
[edit] See also
- Spirostachys africana, a related plant parasitized by a similar moth.
