Locusts figure largely in the Bible: devouring crops, blotting out the sun, laying waste to human endeavours. For us in Britain - last visited by locusts in 1954 when some outriders were blown here from north Africa - they may seem exotic, even picturesque. But for 60 countries in the arid sub-tropical countries of Africa and Asia, the behaviour of schistocerca gregaria remains a matter of anxiety.
Periodically - and unpredictably - overcrowding and hot, dry conditions make desert locusts swarm. Turning from brown to yellow, as many as 80 million per square kilometre take to the air. In the last plague of 1986-89, locust swarms affected an area of more than 29 million square kilometres. Just as in the Exodus, they fly with the wind, up to 130km a day, eating their own weight - two grams - every day. Multiply by 80 million: one tonne of locusts eats the same as 10 elephants.
Why then does the Mauritanian man in the picture look so calm? For Muslims, "Lord of Locusts" is one of the titles of God. As plagues go, it could be worse. Locusts do not attack people or animals, carry no diseases and, in the end, die from cold, or wet or a changing wind. They're also quite tasty and, at 62 per cent protein, commonly eaten, stir-fried, roasted or boiled.
Photograph by JAMES STANFIELDIMAGES
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