Day 6: Locusts buzz, swarm on chemical cue

Adult solitary phase locust; photo by Tom Fayle.

The same chemical that helps turn people and lab mice into crack addicts may also cause locusts to swarm.

A team of researchers from the UK and Australia has discovered that serotonin seems to trigger the swarms of desert locusts, devastating crop pests that span a fifth of the globe.

Serotonin has been found in every multi-cellular organism on the planet. The neurotransmitter is associated with euphoria, agitation and — when it’s lacking — depression in people, which is why many anti-depression drugs act to boost the chemical in the human brain. A serotonin reward leads laboratory mice to hammer cocaine levers like little fiends. And, according to the new research, when serotonin levels triple in the brains of locusts, the insects change from harmless loners into pillaging swarms with billions of individual members.

“It’s really interesting,” study co-author Malcolm Burrows, a zoologist at the University of Cambridge, said in a press release. “Here we have a solitary and lonely creature, the desert locust. But just give them a little serotonin, and they go and join a gang!”

Crops within the gangs’ paths are often devastated, as they have been in recent years in China, Africa, and Australia.

Past studies have pointed to environmental cues that may trigger swarming, like crowding and food shortages. But the researchers say the discovery of an underlying chemical “switch” may open the door to new methods of pest control.

The new study appears in tomorrow’s issue of the journal Science. Michael Anstey, a zoologist at the University of Oxford, is lead author.

Natural serotonin boosters for humans:

• Foods containing tryptophan, an amino acid building block of serotonin
• Foods containing vitamin B-6
• Possibly: exercise
• Source/more information: WebMD

Locust Facts:

• Locusts are grasshoppers that swarm. Of the 8,000 known species of grasshoppers throughout the world only about 12 are swarm-forming locusts.
• An adult Desert Locust is 2-2.5 inches long and weighs 0.05-0.07 oz.
• A Desert Locust adult can consume roughly its own weight in fresh food per day.
• They are prodigious fliers, covering 60 miles in 5-8 hours.
• The two phases are so different in appearance and behavior that they were thought to be separate species until 1921.