Reflections in Nature: Jumping bean’s history goes back to 1857

Recently, I stopped to check to see if the seed pods of the jewelweed plants were ripening, however, none of the seed pods that I picked exploded in my hand, which meant they had not ripened as yet.

If you are wondering what the jewelweed plant is, it is both the red-flecked, orange flower (Impatiens capensis) and the yellow flower (Impatiens pallida) found growing along streams and wet openings. The name Impatiens comes from the way the seeds are jettisoned out of their pods. Jewelweed is a very interesting plant. I like watching the look of astonishment on a child’s face as he or she is introduced to the jewelweed plant. A child’s reaction as the jewelweed seed pod explodes in the child’s hand is a Kodak moment.

The jewelweed plant takes me back to my childhood when my Uncle France, who was quite a jokester, placed a Mexican jumping bean in my hand. The bean jumped in my hand, and wow! I jumped in surprise.

These beans were quite the entertainment for us kids as they jumped around on the palms of our hands.

Perhaps you also remember the surprise of having a Mexican jumping bean in your hand. The bean’s history goes back to 1857 when the insect that puts the jump in the bean was first described and named by the Ashmolean Society of Oxford, England. Although the insect has had several scientific name changes throughout the years, the accepted name is “Laspeyresia saltitans.” The insect is a close relative of our common apple worm. Scientists believe there could be more than one species.

According to the Library of Natural Sciences, the tropical plant that produces the bean is known as Sebastiania pringlei, which is closely related to both the poinsettia and snow-on-the-mountain plants. In Mexico, the jumping bean plant is called “yeba de flecha” and when translated means arrow plant. The name comes from the plant’s poisonous milky sap, which was once used as an arrow and fish poison.

The plant is a shrub that grows to approximately five feet and bears shiny, lance-shaped leaves. The flower spikes appear in early summer when the rain usually comes to this arid land.

At the beginning of the rainy season, the adult moth deposits her eggs in the developing seed pods. In late summer, the three-parted seed pods have matured. After fully developing, the pods dry and snap open. When the seeds inside the pods hit dry brush the sound is similar to BB shots. This is the plant’s way of seed dispersal.

However, not all of the pods have seeds to throw. The seedless pods are those in which the moths had laid their eggs earlier in the summer. The small caterpillars that hatched from these eggs had consumed the contents of the pods.

The pods (or beans), with the caterpillars inside, merely drop to the ground and begin jumping, hence the reason for this jumping comes from the caterpillars. With the hot sun and little vegetation on the ground, the caterpillars inside will die from the heat unless they do something.

The caterpillar has lined the walls of the bean with silk, and as the temperature rises inside, the insect grasps the silken walls with its legs and snaps its body, causing the bean to jump or slightly move. The hotter the temperature, the more the bean jumps, a jump that can be several inches in one hop. If the caterpillar is lucky, the bean will eventually end up in a crevice or under a bush where it is protected from the birds and desert heat.

The caterpillar will live in the bean for six months and continue to jump if the bean becomes too hot. Eventually, the caterpillar cuts a partial opening at the end of the bean; however, a lid remains over the opening. This cutting of the opening is rather amazing because it is never used by the caterpillar. The insect changes to a pupal state, in which it remains until spring. In the spring, the pupa becomes active and pushes through the prepared door. The pupa splits open and out crawls a tiny moth (Carpocapsa saltitans) that soon mates and flies away to lay its eggs in developing seed pods. The yearly cycle begins anew.

However, man interferes with this cycle. The beans are collected in great numbers to be sold in the United States, where they become objects of wonder and amazement. The heat from your hand causes the temperature inside the bean to rise, and the caterpillar jumps.

Since I haven’t seen jumping beans in quite some time, I wondered if it was still legal to bring the beans into the country. I checked and found that the U.S. Department of Agriculture approves the importation of jumping beans into the United States, stating that they pose no danger to our plant life, material goods (clothing) or humans and they are non-toxic.

Just as the peanut is not really a nut and the pineapple is not an apple, not all “beans” are beans. Perhaps the most remarkable of all the beans-that-are-not-really-beans are the Mexican jumping beans, which are actually seeds from a deciduous desert-loving shrub (Sebastiana pavoniana) that only grows in some Mexican states, such as Sonora and Chihuahua.

After hatching out, the fate of these caterpillars is gloomy due to the moths being unable to find their host plants, which means they cannot perpetuate themselves.

Bill Bower is a retired Pennsylvania Game Commission Wildlife Officer. Read his blog and listen to his podcasts on the outdoors at www.onemaningreen.com.


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