Weird and wonderful members of the plant kingdom - Jumping Beans

Jumping beans are commonly sold in novelty shops and by street vendors in Mexico and even if you've never seen one, you've probably heard amazing tales about their erratic movements. 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.

The jumping bean shrubs grow on rocky desert slopes and along arroyos in the region of the Rio Mayo. 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'. Another lesser-known jumping bean shrub is sometimes called the Arizona jumping bean, although it is by no means limited to Arizona. Like many other members of the diverse Euphorbia, or spurge family, 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.

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 light-coloured moth called the jumping bean moth (Laspeyresia saltitans). After consuming the seed within the capsule section, the fat larva has the peculiar habit of throwing itself forcibly from one wall to the other, thereby causing the jumping movements of the capsule. It is believed the larva throws the seed about to break it open and escape. 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.'

Bean photograph by nuala29, used under a creative commons attribution licence