Why Do Mexican Jumping Beans Jump?

   The seeds called jumping beans come from a plant which grows in Mexico. Of course, a jumping bean would not jump if it were only a seed. It is a seed which has become a nursery for a baby moth. The baby moth puts the jump in the bean.
   This is the way a seed is made into a nursery: A female moth lays an egg in the seed when it is just forming. The seed develops around the egg. The plant stores up food for the baby plant in the seed. But the baby plant never gets the food. The moth egg hatches into a tiny caterpillar. It begins at once to eat and grow. It eats all the food in the seed and even the baby plant. Only the seed coat is left. It is like a shell around the caterpillar.
   The caterpillar then lines its "shell" with silk. As it spins the silk it moves from side to side and makes the bean jump. For several months the little caterpillar lives inside the seed. During those months the bean may stop jumping. But the heat from a person's hand may make the insect move and thus make the bean jump again.
   When the caterpillar is about to spin its cocoon, it cuts almost through one side of the bean. The moth that comes from the cocoon has no trouble pushing its way out.
   There are games in which jumping beans are used. One company has sold more than a million beans for use in these games.