Scientists have discovered the trigger that can transform harmless locusts into swarms of billions that decimate crops across the developing world.
They have found that serotonin — a brain chemical also found in humans — lies at the heart of the swarming behavior.
Locusts are normally solitary but they release serotonin when they meet, switching their behaviour from avoidance to aggregation. The researchers crowded locusts together and found that within two hours they began to exhibit "gregarious" behaviour. The more serotonin in a locust's body, the more gregarious it was.
Although there are hopes that the insight may provide clues to controlling swarms, it is unlikely to revolutionise pest control in the long term — chemicals that neutralise serotonin are not designed to penetrate the locust's cuticle or the sheath that encases its nervous system.
And they would have to be applied during the locusts' solitary phase, when they are scarce targets across vast expanses of land.
Researchers need to do more basic research into the locusts' biology, learn more about their serotonin receptors and neurons, and how serotonin interacts with other chemicals to bring about such a significant change in behaviour.
Science 323, 594 (2009)
Science 323, 627 (2009)