They first became famous in the Book of Exodus as the eighth of the 10 plagues of Egypt, but it has taken another few thousand years â€“ and the skills of modern scientists â€“ to work out why desert locusts suddenly swarm in vast numbers.
Desert locusts usually live shy, solitary lives. But every now and again they join together in gregarious bands that actively seek out each other until they form hungry swarms. These can contain a billion or more individuals that each day can devour their own body weight, with devastating consequences for crops and vegetation.
How this dramatic transformation comes about has been a mystery since biblical times â€“ which is why locust plagues were often seen as acts of God. Now scientists have discovered a link to a neurochemical called serotonin, found in the brains of many animals including humans.
A study by the universities of Oxford, Cambridge and Sydney has found a build-up of serotonin in the nerves of the middle part of the locust's body controlling its legs and wings causes, within the space of a couple of hours, the solitary locust to turn into its swarming alter-ego.
The finding opens the possibility of stopping the process long before it happens, by blocking the action of serotonin.