Mexican jumping bean

The beans are considered non-toxic but are not generally eaten. In the spring, when the shrub is flowering, moths lay their eggs on the shrub's hanging seedpods. When the eggs hatch, tiny larvae bore into the immature green pods and begin to devour the seeds. The pods ripen, fall to the ground and separate into three smaller segments, and those segments are called Mexican jumping beans. They move more as temperatures rise. The larva eats away the inside of the bean (until it becomes hollow) and attaches itself to the inside of the bean with silk-like thread. • Illustration — Jumping beans, each about 7 to 10 mm • Illustration — The "trap door" of the jumping bean on the left has been removed, and the one on the right remains attached, next to two moth larvae and their pupal casings. • Illustration — Mexican jumping beans Physicists at Seattle University theorize, using Brownian motion as a model, that the larva's random walk helps to find shade to survive on hot days. Although it does not optimize for finding shade quickly, the strategy minimizes the chances of never finding shade when shade is sparse. 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. In the spring, the moth forces itself out of the bean through a round "trap door," leaving behind the pupal casing. After its metamorphosis, the small, silver and gray-colored moth lives for no more than a few days.

• Illustration — A plastic box of jumping beans sold as a novelty The beans have long been sold in Mexico as a novelty, where they are known as brincadores. The beans featured in comic books from the 1930s through to the 1950s, and have been sold commercially as novelties in clear plastic boxes containing four or five beans. When the bean is warmed (by being held in the palm of the hand, for example) the larva will move to avoid the heat, pulling on the threads and causing the characteristic hop. According to legend, the first person to sell Mexican Jumping Beans was a 12-year-old boy named Joaquín Hernández, from the town of Álamos in the Mexican state of Sonora, in 1921.