Billions of desert locusts in East Africa are swarming at "unprecedented numbers" and pose a huge threat to the region's food insecurity, the UN warns.

The swarms are so bad that Somalia declared a national emergency. Ethiopia and Kenya are struggling to maintain the outbreak, and by Wednesday, swarms have moved over the Arabian Peninsula and reached both sides of the Persian Gulf.

The swarms are a result of heavy rainfall and cyclones over the past two years, which provide ideal environments for rapid breeding.

Photos reveal a skin-crawling look at locust plagues and how menacing they can be.

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Africa's worst locust outbreak in decades is threatening the continent at an unprecedented scope. And there's no telling just how far the ravenous creatures will travel.

Desert locusts are the most destructive of all locust species — known for their speedy growth and enormous appetites. A swarm containing an estimated 200 billion locusts was recorded in Kenya, and each insect can eat its own weight in food. That equates to about as much food as 84 million people a day, according to a UN briefing.

Keith Cressman, senior locust forecasting officer at the FAO, recently returned from northeast Somalia and told Business Insider that the locusts are like "a moving carpet of yellow and black objects" each behaving the same way, and packed together so densely that you can't even see the ground below them.

The insects have already destroyed hundreds and thousands of acres of crops in East Africa, and the UN is calling for international help to quell the crisis. They fear the numbers could grow 500 times by June and reach 30 different countries.

These photos show just how damaging the desert locust can be.