Mexican Jumping Beans

By Margo Jodyne Dills

When I was a little girl, we bought Mexican Jumping Beans at Ye Olde Curiosity Shop on Pier 54 in Seattle. They came in little tiny plastic boxes of three or four greenish-tan beans, about the size of a kernel of corn. These little creatures would roll around inside the box making noise and when I went to bed, I placed them on my nightstand, falling asleep listening to click-click-click. After several days, the beans would begin to turn brown and move less and less. It always saddened me when my dad told me they were dead. My brother and I would hopefully hold them in our hands to warm them and bring them back to life. Sometimes that worked but we usually were disillusioned when Dad told us the worm inside the bean had died.

Years later I learned not only is it not a worm, it isn’t even a bean. It’s a seed capsule containing the larva of a moth that comes from a shrub (Sebastiana pavoniana) that grows in the deserts of Sonora and Chihuahua, Mexico and in some places on the Baja Peninsula. The beans are gathered by Mexican children and eventually sold to novelty shops. (Amazingly, they are very difficult to find anywhere in Mexico.) If they are left in the desert, the larva will eventually cut through the seed wall, build a cocoon and metamorphose into a beautiful moth (laspeyresia saltitans). It is said the shaking of the young beans scares the birds away and effectively protects the process. The moths deposit their eggs in the shrubs to begin the cycle once again.

A lesser know fact is that these fascinating toys come from the same plant that produces the sap that natives once used to poison their arrows, which gives the shrub another name: yerba de la flecha (herb of the arrow.)