A single locust can eat its own weight each day

The insects have devastated crops across West Africa in recent months.

Experts of the UN's Food and Agriculture Organisation (FAO), meeting in Senegal on Monday, said the insects were moving north to breed.

They predict that the swarms will expand next year in Morocco, Algeria, Tunisia and Libya, then move south.

The FAO representative in Senegal, Edouard Tapsoba, said the situation could last for a couple of years.

"We should not think we are at the end of the story," he said.

This year's locust plagues have been the worst in a decade.

Locusts remain in Mauritania, Senegal, Niger and Mali, but the focus of prevention efforts in the coming months will be Morocco, Tunisia, Algeria and Libya, officials said.

Said Ghaout, an FAO consultant who is the director the national locust control centre in Morocco, said a new generation of locusts was expected to breed in November in Mauritania and northern parts of Niger.

Those swarms will move in January to northern Africa, where they will breed in March or April then move south again in June, Mr Ghaout said.

EU representative Jos Van Aggelen told a news conference: "It's clear that this year we have not won this battle against the locusts."

"It's important that we're better prepared next year for this fight," he said.

The FAO has appealed for $100m to tackle the crisis but so far has received much less.