Jumping bean, the seed of a Mexican shrub, is famous for its quick, jumping movements. The movements of a jumping bean are actually caused by a caterpillar that lives inside the seed. Moths of the species Laspeyresia saltitans deposit their eggs in the shrub’s flowers. After the eggs hatch, the caterpillars burrow into the young seeds of the shrub. The seeds later develop a hard outer wall that conceals any indication of how the caterpillar entered.
The caterpillar eats away the inside of the seed, but it leaves the seed wall undamaged. The insect then builds a web along the inner wall. The seed jumps when the caterpillar grasps the web and jerks its body. Scientists believe the jumping helps scare away animals that might try to eat the seeds. Jumping beans remain active for several months. Then the caterpillar makes a circular lid by cutting through the seed wall. The caterpillar later forms a cocoon and begins to change into a moth. When the change is completed, the adult moth pushes through the lid and leaves the seed.
