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The seed of the Sebastiania plant contains tiny larvae of the Cydia saltitans moth, also known as the jumping bean moth. As these larvae grow, they cause the seed to move and jump. Brett Hondow/ShutterstockFor those who spent their childhood in southern California, visits to 7-11 often included spotting Slurpees, gum, and small transparent boxes filled with four or five Mexican jumping beans. The rattling sound of the beans hitting the plastic boxes was unmistakable. Many parents bought these beans, allowing kids to enjoy playful activities on the kitchen table. But what exactly triggers the jumping motion in these beans?
What Is a Mexican Jumping Bean?
Despite their name, Mexican jumping beans are not actual beans; they are seed pods from the Sebastiania pavoniana shrub. These pods, roughly the size of a corn kernel, house a tiny larva called Cydia saltitans, or jumping bean moth, which is the reason behind the bean's unusual movements.
The Life Cycle of the Cydia Saltitans Moth
The process begins when a female Cydia saltitans moth deposits her eggs on the young green pods of the Sebastiana shrub. Within weeks, the eggs hatch, and the insect larvae (worms) burrow into the pod, consuming the seeds inside. These larvae, no bigger than a grain of rice, start feeding on the pod's contents immediately.
Why Do Mexican Jumping Beans Jump?
Several theories explain why Mexican jumping beans move, but most suggest the motion occurs when the larvae inside contract and spasm, striking the seed pod and creating the erratic jumping. These larvae can live for months, periodically contracting and relaxing, which keeps the bean in motion. Some theories propose that the larvae move to escape high temperatures and sunlight, which could be fatal, ensuring they survive long enough to reach the pupal stage.
Following months of development and movement, the moth larvae enter a brief dormant phase, during which they spin cocoons inside the seed pod. They then undergo metamorphosis, eventually emerging as adult Cydia saltitans moths. These moths vanish into the desert, and the cycle begins anew, producing the next generation of Mexican jumping beans.
Where Do Mexican Jumping Beans Come From?
The town of Alamos, Sonora, in Mexico, is known as the "Jumping Bean Capital of the World" due to its status as the main supplier of Mexican jumping beans. The Sebastiania shrub, which produces these distinctive seed pods, is indigenous to the area. Locals gather the pods containing the tiny moth larvae and sell them globally as unique curiosities.
Although Mexican jumping beans are safe and nontoxic, they are not typically consumed, as they are not actual beans.
