Locusts have formed plagues since prehistory. The ancient Egyptians carved them on their tombs and the insects are mentioned in the "Iliad", the Mahabharata, the Bible and the Quran. Swarms have devastated crops and been a contributory cause of famines and human migrations. More recently, changes in agricultural practices and better surveillance of locations where swarms tend to originate have meant that control measures can be used at an early stage. The traditional means of control are based on the use of insecticides from the ground or the air, but other methods using biological control are proving effective.