A devastating outbreak of locusts is spreading across East Africa, threatening millions of people with hunger.<br/> The insects are travelling in huge swarms that can be as big as some major cities, sometimes about 1.5 times the size of New York City. Locusts have destroyed crops in Somalia, Ethiopia, Kenya and have now made their way to Sudan. These are places that’s already extremely vulnerable to famine. Experts say a prolonged period of wet weather, including several rare cyclones that struck eastern Africa and the Arabian Peninsula over the last 18 months, led to the locust outbreak. But it is not over yet. In East Africa, more rains in the coming weeks will create a suitable breeding ground for the locusts. Officials say the number of overall locusts could grow up to 500 times by June, when drier weather begins. But what is a swarm and how does it start? Here's our explainer.
