In the fall of 1923, street vendors in Santa Barbara, California received an unexpected bit of attention regarding one of their more popular wares: The San Francisco Chronicle wrote about the sellers' “freakish little brown seeds” that “cavorted about to the edification and delight of children and grownups."
Those “freakish” seeds were (and still are) known as Mexican jumping beans. Part novelty item and part entomology lesson, they’ve been a staple of street vendors, carnival workers, and comic book ads for nearly a century, thanks to their somewhat inexplicable agility. Some early theories posited that the beans moved because of electrostatic charging, or because of tiny gas explosions inside—but in reality, it was a larva living in the bean. In Santa Barbara, the local Humane Society was concerned that the tiny caterpillar was somehow suffering in the heat; a police sergeant confiscated several of the seeds and took them home to investigate.
THE BEAN MYTH
In truth, the bean is not really a bean at all but a seed pod. In the spring, adult moths deposit their eggs into the flower of the yerba de flecha (Sebastiana pavoniana) shrub, which is native to the mountains of northwestern Mexico. The hatched larvae nestle into the plant's seed pods, which fall off the tree, taking the larvae inside with them.
Each larva is quite content to remain in its little biosphere until it enters its pupal stage and eventually bores a hole to continue life as a moth. (But only when it’s good and ready: If the pod develops a hole before then, the caterpillar will repair it using natural webbing it makes.) The pod is porous and the larvae can eat the interior for nourishment. Metabolic water creates moisture for the larva, but it never needs to pee. Essentially, it's the ultimate in downsized efficiency living.
When it's in the pod, the larva isn’t exactly dormant: It twists and contorts itself to create encapsulated movement, almost like the snap of a rubber band. When it moves, so does the pod. No one is exactly sure why they do this, though some believe it's to keep the pod from settling on a hot surface (as high temperatures can be deadly to the insect).
The larva will keep up this activity for six to eight weeks. If a pod appears lifeless and rattles when shaken, it’s probably dead. If it lives, it will go dormant in winter before creating an escape hatch in the spring and flying off to begin life as a moth.
It’s hard to know who exactly first decided to begin hawking the “beans” for amusement purposes, though some credit an enterprising man named Joaquin Hernandez with popularizing them in novelty shops in the 1940s. Later, in the 1960s, Joy Clement of Chaparral Novelties noticed the beans after her husband, a candy wholesaler, brought them home from a business trip. Though she was initially confounded by their appeal, Clement agreed to distribute the pods and watched them grow into a significant success: Between 1962 and 1994, Chaparral shipped 3 to 5 million of them each year, and saw the bean transition from sidewalk dealers to major chains like KB Toys.
“There's not much you can buy at a retail store that can give you this kind of satisfaction for under a buck," one bean dealer told the Los Angeles Times in 1994. "It's one of the last of the low-end entertainments available in the world.”
Interest in the beans seems to come in waves, though that can sometimes depend on the weather in Mexico. The jumping bean's unusual insect-crop hybrid stature means that farmers in Álamos, Sonora—where the pod is harvested and remains the area's major export—rely heavily on ideal conditions. Lowered rainfall can result in lower yields. Álamos typically handles more than 20,000 liters of the pods annually. In 2005, thanks to unfavorable weather, it was just a few hundred.
There have been other issues with marketing hermetic caterpillars for novelty purposes. A UPS driver once grew nervous that he was transporting a rattlesnake thanks to a shipment of particularly active pods. Bomb squads have been called in on at least two occasions because the noise prompted airport workers to believe a ticking explosive device was in their midst. And then there was the Humane Society, which remained dubious the beans were an ethical plaything. (Since the caterpillars repair breaches to the pod, the reasoning is that it seems like they want to be in there, though no one can say whether the insects enjoy being handled or stuffed into pockets.)
You can still find the beans today, including via online retailers. They’re harmless and buying them as "toys" is probably not harmful to the caterpillar inside, though the standard disclaimer warning owners not to eat the beans remains. The police sergeant in Santa Barbara found that out the hard way: After taking his nightly prescription pill, he felt an odd sensation and went to the hospital. After physicians pumped his stomach, they noted that he had accidentally consumed a jumping bean. In his digestive tract, it was leaping to get out.