Jumping beans are one of the curiosities the north of Mexico displays for tourists. It looks like magic, but there is an explanation for everything. Also for jumping beans or "frijoles saltarines" as they're called there.

Each year, 20 million leapers of a more playful kind arrive in the world’s toy shops from a tiny part of Mexico.

The jumping bean is really the seed of a desert shrub. Only a few show this odd leaping.

The seeds, imported as novelty toys, seem to have a mind of their own.

There really is a mind behind the jumping: a moth caterpillar lives and feeds inside the seed.
 
The caterpillars flip their home to escape. They not only feel the heat, light makes them jumpy.

They fuss and fidget into the shade. This behaviour is a lifesaver in the hot Mexican desert.

The caterpillar repairs the damage by weaving a silken wall.

It grips on to the silk wall when it leaps. And the shape of the bean helps it roll.

For weirdness, the Mexican jumping bean is hard to beat.

LEAPERS= The verb “to leap” means “to jump”, so “leapers” here refers to things that jump.

PLAYFUL= Full of high spirits and fun; someone who likes to play.

TINY= Very small.

BEAN= A grain of a plant used for eating (see picture here).

SEED= The part of a plant that you put in the ground and water to make a new plant grow.

SHRUB= A woody plant, smaller than a tree, with several stems instead of a trunk (similar to a bush). See picture here.

ODD= Strange.

A NOVELTY= Something new.

(THEY) HAVE A MIND OF THEIR OWN= They think and take their own decisions.

FEEDS= Eats.

FLIP= Turn over.

JUMPY= Prone to jump, nervous, easy to scare.

FUSS= To get nervous and move around a lot.

FIDGET= To behave or move nervously.

THE SHADE= An area in the shadow.

THEY FUSS AND FIDGET INTO THE SHADE= They move quickly and nervously to roll back into the shade and away from the dangerous heat of the sun.

A LIFESAVER= Something that can save your life.

DAMAGE= Harm or injure.

WEAVE= To make cloth by crossing and intertwining threads. For example, if you want to make a sweater with wool, you take the wool and weave it using two large needles.

SILKEN= Made of silk.

THE CATERPILLAR REPAIRS THE DAMAGE BY WEAVING A SILKEN WALL= We use BY + -ING to express how we manage to do something.
- She was in the kitchen making sandwiches –this is what she was doing
- She helped me in the kitchen by making sandwiches ---this is how she helped me (she made sandwiches in order to help me).
- I saw him climbing up a wall ---this is what he was doing
- I saw him by climbing up a wall ---this is how I could see him, it’s what I did to see him (I climbed a wall in order to see him).

GRIP= To grip is to hold tight, to grasp firmly.

ROLL= Turn around.

WEIRDNESS= Something weird /wɪəd/ is strange, odd. Weirdness is the quality of being weird.