MEXICAN JUMPING BEAN
The Mexican jumping bean is a peculiar phenomenon to Mexico. However, if you are in Mexico and wish to observe/purchase some Mexican jumping beans, asking the locals for 'Mexican jumping beans' will result only in blank faces. And don't think that you should be asking for 'Jumping Beans' as you are already in Mexico and will not need to differentiate them as such - because more blank faces will ensue. Why? Because Mexican jumping beans are known as Frijoles saltarines in Mexico! So now you know.
What are Mexican jumping beans?
Physically, Mexican jumping beans resemble small beans, tan to brown in colour. They are a seed pod through which the larva of a small moth has chewed (Cydia deshaisiana). The bean "jumps" because, when it gets in a hot place, the larva snaps its body hoping to roll to a cooler place. The beans are from a shrub often referred to as the jumping bean.
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. Normally, in the spring, the moth will force its way out of the bean through a round "trap door", leaving behind the pupal casing. The small, silver and gray-colored moth will live for only a few days.
The larvae jump as a survival measure in order to protect themselves from heat, which can cause them to dry out. The heat from the sun stimulates them to jump, even in cool temperatures. Leaving the beans in the sun for extended periods, however, will dehydrate and kill them.
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