Farmers have a largely unappreciated friend. It is the Bat. At the Annual Walnut Research Conference in Bodega Bay, California, USA, researchers said that bats help to keep the skies above farms free of insect pests. One example is the codling moth, which causes considerable harm to pear, apple and walnut crops in California. Rachael Long and Bronwyn Hogan of the University of California in Yolo County found that pear groves suffer less than 5 per cent damage when a colony of bats lives less than a mile (1.6 km) away. However, if the nearest bat colony is two miles (3.2 km) away, crop damage rises to a whopping 60 per cent. The researchers have recorded individual bats eating an insect every two minutes. "This is the first study that shows bats forage quite extensively on farms,' says Long, who has built artificial bat houses.