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Saturday, November 10, 2012

Creature Feature: Mexican Jumping Beans.

In Texas, every souvenir shop has something made out of a weird, dead animal. Hotlix are everywhere. Quite a few places had longhorn cow skulls. Leather exists there- very good leather. One of the most bizarre, however, just so happens to be quite common: the Mexican jumping beans. 



The beans actually 'jump' thanks to the larva of a moth called Cydia deshaisiana, or the "Mexican jumping bean moth." As per the name, they are native to Mexico and the southwestern United States. There are actually a number of shrubs, and a number of moths, that can make "jumping beans," but for now we will focus on the kind sold in random tourist junk shops.

The larval moth spends its entire life in the seed capsule (not bean) of a Sebastiana plant. An adult  C. deshiasana lays an egg on the seed, and the larva burrows in shortly after. If the seed is cracked, the little creature uses silk to repair it. The bean, if nothing else, is a source of food and shelter all at once. Not a bad home if you happen to be a caterpillar.

The "jumping" in jumping beans happens when the larva has eaten all of the inside of the bean. Then, for no explicable reason, they begin pulling silk around the inside of the bean, causing it to roll and fidget if not jump. They jump as an attempt to regulate their body temperatures - it's hot down south!



 Of course, the jumping bean larva cannot stay inside the bean forever. It pupates inside bean, meaning that the frail adult moth will have a hard time getting out. To escape, the larva forms a "trap door" in the bean- a small, round hole that it can push its way out of. This small hole is sometimes marketed as well, even though it defies the point of a jumping bean.

The adult moth is a small, gray, unimpressive creature. It's one of those bugs that reaches maturity only to mate; it doesn't even have jaws. In the span of a few days, it must mate, find an immature Sebastiana seed, and lay eggs. Thus the cycle of touristy crap begins again...but look on the bright side: other, related moths do this to seeds we actually eat.

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