The desert locust is the most destructive insect in the world. One swarm may cover 1000 square kilometres, and consists of up to 250 billion individuals. Although a locust weighs only 2 grams, in its gregarious phase it will eat its own weight in food every day. it is therefore essential to recognise a potential swarm as early as possible. In 1992 a new satellite-based surveillance system came into operation for Africa. This has dramatically improved the speed with which news of approaching swarms reaches threatened communities.