Mexican jumping bean

A Mexican jumping bean is an occurrence native to Mexico, where it is known as a brincador ("hopper"). Physically, Mexican jumping beans resemble small tan to brown beans. They are a seed pod through which the larva of a small flea has chewed. The seed does not actually jump so much as wiggle because when it gets in a hot place the larva snaps its body hoping to roll to a cooler place. The beans themselves are from a shrub of the genus Sebastiania (S. palmeri or S. pavoniana), itself often referred to as the jumping bean, while the Jumping Bean Moth (Cydia deshaisiana) is a member of the large genus Cydia.

Life cycle

• Recording of a Mexican jumping bean in motion.
• 
  Bean showing the "trap door" and discarded pupal casing

After the egg hatches, the larva eats away the inside of the bean, making a hollow for itself. It attaches itself to the bean with many silk threads.

The larva may live for months inside the bean with varying periods of dormancy. If the larva has adequate conditions of moisture and temperature, 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.

The larvae jump as a survival measure in order to protect themselves from heat, which can cause them to dry out. The heat from the sun stimulates them to jump, even in cool temperatures, but leaving the beans in the sun for extended periods will dehydrate and kill them.

Playing with/testing the beans

Jumping beans are still widely available for sale in the United States (see links below). In the UK, they were a common novelty item in the 1950s. They are a popular scientific and classroom project even now. 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 bean does noticeably move around.

The beans should become active if one holds them in the hand (out of the box) for a few minutes. The beans should also appear to be a very slight shade of green on the side (as shown in the bean in the top picture, on the right). If the bean starts to turn brown (top picture, bean on the left), that indicates it is dying. If one shakes a bean near one's ear and hears a rattle inside, the larva inside has either died, or entered the pupal stage, where its hardened shell makes a softer rattle.

A plastic toy under this name was manufactured and sold in packages containing several devices in the 1960s. It resembled a "time release" capsule and had a metal ball inside. When the surface on which the capsule was laid was tilted, the ball would roll to the other end and make the capsule twitch.

Maintenance — "watering" and storage of the beans

To rehydrate the beans, they need to be soaked, not submerged, for a three-hour period in chlorine-free water once or twice a month. The chlorine found in tap water in some locales will kill them. Alternatively, one may let chlorinated tap water stand in an uncovered glass for about six hours before using, to let the chlorine dissipate. Just spraying the beans with a little water is ineffective in maintaining the larvae's lifespan. Beans should be stored in a cool, dry place, but freezing will kill them.

If beans are shaken too hard, they will sometimes stop movement for a short amount of time as a defense mechanism.

Source of the beans

The Mexican jumping bean comes from the mountains in the states of Sonora, Sinaloa, and Chihuahua; indeed, Álamos, Sonora styles itself the "Jumping Bean Capital of the World". They can be found in an area approximately 30 by 100 miles where the Sebastiana pavoniana host tree grows. During the spring, moths emerge from last year's beans and deposit their eggs on the flower of the host tree.

Jumping beans in popular culture

Jumping beans were used as a recurring gag in many cartoons from the 1930s to the 1950s, wherein eating the beans would cause a character's whole body to bounce out of control and land on something painful.

Jumping Beans are accidentally eaten by the titular character in the Scooby Doo, Where Are You! episode "Which Witch is Which?", first aired in 1969.

See also

• Spirostachys africana, a related plant parasitized by a similar moth.

External links

• Description of jumping beans
• Video clip of jumping beans "jumping" (Shockwave Flash format)
• "The Jumping Bean's Life Cycle"
• Wholesale And Retail Supplier Of Mexican Jumping Beans
• Mexican Jumping Bean humor