What Makes Jumping Beans Jump?
Jumping beans are made to jump by the action of little insects inside them. The beans are the long seed of certain Mexican shrubs and contain the larvae or caterpillars of a small species of moth with large scientific name of Carpocapsa saltitans.
The second of these two Latin words means jumping. The larvae are stirred into movement by warmth, and it is this activity that makes the beans jump.
The “bean” is usually tan to brown in color. It “jumps” in an attempt to roll the seed to a cooler environment to avoid dehydration and consequent death. They are from the shrub Sebastiania pavoniana, often also referred to as “jumping bean”.
However, they are not related to actual beans (legume plants), but rather to spurges. The beans are considered non-toxic but are not generally eaten.
After the moth-laid egg on the plant hatches, the larva eats away the inside of the bean (until it becomes hollow) and attaches itself to the inside of the bean with silk-like thread. The larva may live for months inside the bean with varying periods of dormancy.
If the larva has adequate conditions of moisture and temperature, it will live long enough to go into a pupal stage.
In the spring, the moth forces itself out of the bean through a round “trap door”, leaving behind the pupal casing. After its metamorphosis, the small, silver and gray-colored moth lives for no more than a few days.