Cannibal theory for locust swarms

By Ben Lowings
BBC News

A swarm of locusts can devour as much food as 2,500 people

Scientists say they may have discovered the reason why swarms of locusts are driven to devour such huge quantities of vegetation.

They suggest that locusts combine into swarms because they are frightened of being eaten by each other.

The findings by researchers from the US, UK and Australia were published in the journal Current Biology.

A swarm can contain billions of insects and eat tens of thousands of tonnes of vegetation in a single day.

Find out about the locust's life cycle

Sounding like waves of rain, it darkens the desert sky and descends to destroy swathes of food crops.

It is a chilling sight for farmers in many of the world's poorest countries.

Fields are stripped bare. It has a huge impact on food supplies for whole countries.

Seen eating each other

No-one is sure exactly what makes locusts swarm in this way.

They are usually herbivores but scientists have observed them eating each other.

This is when they cannot get hold of enough food when normal supplies start to run short.

Young locusts, which cannot fly, have been seen eating other members of their group.

The new theory suggests that some other locusts start to panic.

Increasing numbers of locusts band together to try to get away from the hungry cannibals chasing behind.

They keep this momentum when they reach the adult phase of their life cycle and take to the air.

The study's authors hope their work will contribute to understanding when, where and why these bands of young locusts form.

This, they say, will be crucial for controlling locust populations and, ultimately, for warding off disasters for people.

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