Posted on behalf of Roberta Kwok

News outlets are swarming around a new study showing how locusts form giant hordes that can wreak havoc on crops.

The key is serotonin, a brain chemical that influences moods in humans. Now, researchers have shown that it also changes “what are essentially large grasshoppers living in the desert into swarming, destructive pests”, says co-author Stephen Rogers at the University of Cambridge, UK (Reuters).

Previous studies have shown that locusts will start swarming at the sight and smell of other locusts or the tickling their hind legs receive from bumping against their compatriots. As reported in Science, the team found that the locusts’ serotonin levels went up when the insects crowded together. Locusts injected with serotonin-blocking drugs stayed to themselves, while solitary locusts treated with extra serotonin underwent a “Dr. Jekyll to Mr. Hyde transformation” and formed swarms (AP).

The serotonin boost during swarming would be “pharmacologically similar to being on antidepressants, and on Ecstasy”, says co-author Stephen Simpson of the University of Sydney in Australia (Science News).

Locusts have plagued humans through the ages and are still afflicting China, Australia, and Africa. A swarm 3.7 miles long feasted on crops in Australia last year (Independent), and Africa spent $400 million in 2004 to wipe out the pests (Reuters).

The study could help scientists devise new eradication strategies by, for instance, blocking the insects’ serotonin receptors. But the treatment would need to be applied while the locusts are still solitary, which might be more difficult than the current method of blasting huge swarms with pesticides (National Geographic News).

Images: left: gregarious phase locust / right: solitarious phase locust both copyright Tom Fayle.