Not content with being a Biblical plague, locusts have given us another reason to despise them. According to researchers from the US, Australia and the UK the actual reason they swarm has a horrific cause: they’re cannibals…

In a new paper in Current Biology Iain Couzin and colleagues suggest that mass locust migrations are driven by “abdominal biting and the sight of others approaching from behind”. Basically, when they get hungry young locusts start to bite each other, those bitten start to run away. Others get spooked and the sight of another locust approaching sets them off (paper abstract, BBC coverage).

In their paper the researchers report that ‘abdominal denervation’ reduces the probability that individuals will start moving and increases cannibalism. Occluding their rear vision has similar impacts.

“Cannibalism is rife within marching bands of locusts,” says Couzin (press release). “No one knew until now that cannibalistic interactions are directly responsible for the collective motion exhibited by these bands.”

As young locusts often precede flying swarms of adults, which are harder to kill, knowing what causes their movements could help in controlling them he says.

Image: USFWS