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What Makes Those Jumping Beans Jump?

The jumping bean shrub Euphorbia is a member of the spurge family. Mexican jumping beans intrigue us because we don't understand how this inanimate object could actually jump, even though we see it with our own eyes. It is the question everyone wonders when they see the jumping beans. We think to ourselves, is it alive or are there strings attached making it jump? Well, neither of these theories are correct. Our curiosity of the special beans sparks our fascination of why they jump. Mexican jumping beans are grown in Mexico on a type of shrub. The shrub grows in sandy or rocky soils. It is also grows in the wild on some islands in the Gulf of California. The jumping bean shrub is a member of the Euphorbia Family and produces a milky, poisonous substance in its stems. Its leaves are a shiny, bright green and turn red in winter.

Jumping beans are not actually beans, or seeds. It is actually a section of a seed capsule. So what makes them jump? Interestingly, Laspeyresia saltitans, a small gray moth, inserts its larva into the seed capsule. The larva eats the inside of the jumping 'bean' and flings itself from one wall to the other. This is what causes the bean to jump. Once the moth inserts her larva into the seed and it becomes a 'jumping bean', the plant cannot reproduce from that seed. Not all of the seeds have a larva inside of them, which is a good thing for the population of the jumping bean shrub.

Jumping beans are usually only sold seasonally, from July to September. The moth inserts her larva in early spring, which gives it time to eat the inside of the seed. If you ever buy a Mexican jumping bean, remember that there is something very much alive in it and it doesn't jump forever. Eventually, the larva runs out of food. You'd think with all that jumping around the poor larva would have a headache!


About the Author

Rebekah ShafferRebekah Shaffer
Rebekah Shaffer is currently a Junior at Slippery Rock University, PA. She is pursuing her B.S. in Biology, minor in Chemistry. She currently works as a microbiology lab assistant at Slippery Rock University and is a member of Beta Beta Beta Biology Honorary Society. She plans to obtain her Ph.D. in Molecular/Cellular Biology after completing her undergraduate degree.

Further Reading
Smithsonian Handbooks: Butterflies and Moths
by David J. Carter, Frank Greenaway (Photographer)

Related Web Links
What Exactly Are Mexican Jumping Beans?

Nature's Jumping Beans
by Iziko Museums of Cape Town

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