The vast southwest desert region of North America contains many fascinating wild plants, but none are more intriguing than the Mexican jumping bean. Jumping beans are commonly sold in novelty shops and by street vendors on both sides of the border, and probably everyone has marveled at their erratic movements, or heard a fabulous tale about them. In the regions where they grow wild, they are often collected by children and sold to local dealers who export them to the United States. The actual jumping "bean" is not a bean at all. It is produced by a native shrub or small tree that grows wild in the deserts of mainland Mexico and in the rugged Cape region of Baja California.

An assortment of Mexican jumping beans. They are actually the separate sections (carpels) of seed capsules from the Mexican shrub (Sebastiana pavoniana).
The common jumping beans sold in novelty shops throughout the southwestern United States come from a deciduous shrub (Sebastiana pavoniana) with dark green, leathery leaves that turn red during the winter months. The jumping bean shrubs grow on rocky desert slopes and along arroyos in the region of the Rio Mayo in the states of Sonora and Chihuahua. One of the best places to see this shrub is in the vicinity of Alamos, Mexico, known locally as the "jumping bean capital of the world." Mr. WOLFFIA (the editor of WAYNE'S WORD) recently photographed this interesting shrub in canyons of the Sierra de la Laguna in the Cape region of Baja California. By late winter the shrubs become a blaze of red, in sharp contrast with the beautiful green fan palms (Erythea brandegeei). Another lesser-known jumping bean shrub (Sapium biloculare) is sometimes called the Arizona jumping bean, although it is by no means limited to Arizona. The Arizona jumping bean occurs along washes and rocky slopes from the vicinity of Ajo, Arizona, south through the desert areas of Sonora, Mexico and Baja California. It also occurs on some of the islands in the Gulf of California. Like many other members of the diverse Euphorbia Family (Euphorbiaceae), freshly cut stems of both species of jumping bean shrubs exude a poisonous milky sap. In fact, several tribes of native Indians reportedly used the sap to poison their arrow tips. In Mexico the shrubs are sometimes called "yerba de la flecha," which translated means herb of the arrow.

Showy red clumps of Mexican jumping bean shrubs (Sebastiana pavoniana) and stately fan palms (Erythea brandegeei) dot a canyon bottom of Sierra de la Laguna in the rugged Cape region of Baja California.
Probably the most interesting thing about Mexican jumping bean shrubs are the remarkable "beans" that jerk and roll about with seemingly perpetual motion. It is doubtful (or very rare) that they actually "jump" above the surface of the ground, but they can certainly roll and tumble along in different directions. Just as pineapples are not apples and peanuts are not nuts, the jumping bean is not a bean, nor is it a seed. It is actually a small, thin-shelled section of a seed capsule containing the larva of a small gray moth called the jumping bean moth (Laspeyresia saltitans). After consuming the seed within the capsule section, the robust, yellowish-white larva has the peculiar habit of throwing itself forcibly from one wall to the other, thereby causing the jumping movements of the capsule. Mexican jumping bean capsules typically separate into three parts or sections, some of which contain a moth larva. It is these separate sections (technically called carpels) that are sold as "jumping beans."