The cockchafer overwinters in the earth at depths between 20 and 100 cm. They work their way to the surface only in spring. Because of their long development time as larvae, cockchafers appear in a cycle of every three or four years; the years vary from region to region. There is a larger cycle of around 30 years superimposed, in which they occur (or rather, used to occur) in unusually high numbers (10,000s). Both the grubs and imagos have a voracious appetite and thus have been and sometimes continue to be a major problem in agriculture and forestry. In the pre-industrialized era, the main mechanism to control their numbers was to collect and kill the adult beetles, thereby interrupting the cycle. They were once very abundant: in 1911, more than 20 million individuals were collected in 18 km2 of forest. Collecting adults was an only moderately successful method. In the Middle Ages, pest control was rare, and people had no effective means to protect their harvest. This gave rise to events that seem bizarre from a modern perspective. In 1320, for instance, cockchafers were brought to court in Avignon and sentenced to withdraw within three days onto a specially designated area, otherwise they would be outlawed. Subsequently, since they failed to comply, they were collected and killed. (Similar animal trials also occurred for many other animals in the Middle Ages.) In some areas and times, cockchafers were served as food. A 19th-century recipe from France for cockchafer soup reads: "roast one pound of cockchafers without wings and legs in sizzling butter, then cook them in a chicken soup, add some veal liver and serve with chives on a toast". A German newspaper from Fulda from the 1920s tells of students eating sugar-coated cockchafers. Cockchafer larvae can also be fried or cooked over open flames, although they require some preparation by soaking in vinegar in order to purge them of soil in their digestive tracts. A cockchafer stew is referred to in W. G. Sebald's novel "The Emigrants". Only with the modernization of agriculture in the 20th century and the invention of chemical pesticides did it become possible to effectively combat the cockchafer. Combined with the transformation of many pastures into agricultural land, this has resulted in a decrease of the cockchafer to near-extinction in some areas in Europe in the 1970s.