Why Mexican Jumping Beans Jump

THEY are fascinating to watch. When laid on a flat surface, the beans will roll from side to side, turn over endwise, or actually jump as if alive. The sight is so incredible that some persons have thought magic or spiritism might be involved. Is this so? What makes the beans jump?

It is only a certain type of bean that will jump. These beans are seeds of a Mexican shrub of the spurge family. The shrubs grow ten to twenty feet high, and the seeds come three to a pod, each being less than a third of an inch long. They have two flat sides and the third is convex, so they appear somewhat three cornered in shape.

The shrubs bearing these seeds grow wild in the foothills and mountains near the small town of Alamos, in the south of the Mexican state of Sonora. Residents had long known about the seeds and their unusual jumping ability. Years ago youngsters would sell them to the few visitors to the area.

“An American found Alamos in 1921,” explains Joaquin Hernandez, who was just a youth at the time. “He was fascinated with the jumping beans. He said he would buy as many beans as I could supply him so he could sell them to other Americans. I got every kid in town to help me.”

That was the beginning of a jumping-bean industry that now thrives in the area. “Everybody in Alamos harvests the beans,” says Hernandez. “If a person gets lucky he will earn as much as 200 pesos ($16) in one day of picking.” The beans are brought to Hernandez’ hacienda, where some sixty girls are employed to prepare them for shipping. In a good year, more than 30 million jumping beans are harvested.

“Only a few of the beans stay in Mexico,” explains Hernandez. “Most Mexicans have never heard of jumping beans. Just the people around here know them, and the people in the border towns who see them for sale.” This is because most of the beans are exported.

“Half the jumping beans I ship by rail to the United States,” notes Hernandez, who has a monopoly on the industry. “About 40% are flown to Europe, almost 10% to Japan and several thousand to the Mexican border towns.”

A simple examination reveals the secret of the fascinating twisting, turning and jumping of the beans. Inside each bean is a tiny yellow caterpillar, the larvae of a small moth. How does it get there? The moth lays an egg in the flower of the spurge shrub. In time the eggs hatch and the larvae are said to work their way deep into the blossom, where they are eventually encased in the seeds.

The caterpillar devours a large part of the inside of the seed, so that it occupies about one fifth of the interior of its little home. To move the bean, the caterpillar grasps the silken wall of the bean with its legs and vigorously snaps its body, striking its head against the other end of the bean and sending it this way or that. The bean may actually travel several inches at a time, or leap in the air. Some people call them bronco beans because of the way they jump.

“We don’t know why the worm inside is so restless, but we are glad he is,” says Hernandez. “He isn’t trying to get out. We know that for sure. If the shell is shattered, the worm inside immediately goes to work to mend it with a silk secretion. When he patches up his house, he starts jumping again with as much vigor as before.”

A jumping bean may keep up its antics for as long as six months. Then the caterpillar finally emerges from its house and becomes a moth.

It is in June and July that the bean harvest takes place around Alamos. After the beans are brought in, the girls count them and individually shake each bean. If one rattles, that means the caterpillar inside is dead, and the bean is thrown away. The beans must breathe to survive, so they are put in special tins punctured with holes for shipping.

So it is obvious that no magic or spiritism is connected with the antics of these jumping beans. They are simply a feature of Jehovah God’s marvelous creation that is fascinating to man.