YOUNG: It’s Living on Earth. I’m Jeff Young.

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Coming up – a new tool to help you shop greener – but first, this note on emerging science from Lindsay Breslau.

BRESLAU: A small, green grasshopper sits alone on a blade of grass, innocently munching on the juicy stalk. It seems harmless, but beware. One day it may join a gang.

In 1921, scientists discovered that the green desert grasshopper is the same species as the destructive, yellow and black locust. But the split personality of the creature remained a mystery.

Recently, a group of researchers from Britain and Australia linked this behavior transformation to serotonin, a brain chemical found in all complex organisms. They discovered that the nervous systems of swarming locusts contain three times as much serotonin as solitary locusts.

By tickling a grasshopper's hind legs to simulate jostling by other locusts, the scientists could transform the solitary insect into a social creature within hours. To test their theory, they injected a serotonin inhibitor before tickling the legs and found no behavior change. But when the researchers injected a serotonin promoter and didn't stroke the insects, they changed color, grew large muscles, and behaved gregariously.

During droughts, locusts are forced into small areas to look for food. Close contact with other locusts causes this chemical change, creating swarms that can number in the billions.

Scientists hope that this discovery about serotonin will lead to research on how they could rehabilitate the violent gangs of locusts and turn them back into harmless grasshoppers.

That's this week's note on emerging science. I'm Lindsay Breslau.