Drosophila circadian rhythm is a daily 24-hour cycle of rest and activity in the fruit flies of the genus Drosophila. The biological process was discovered and is best understood in the species Drosophila melanogaster. Other than normal sleep-wake activity, D. melanogaster has two unique daily behaviours, namely regular vibration (locomotor activity) during the process of hatching (called eclosion) from the pupa, and during mating. Locomotor activity is maximum at dawn and dusk, while eclosion is at dawn. Biological rhythms were first studied in Drosophila. Drosophila circadian rhythm have paved the way for understanding circadian behaviour and diseases related to sleep-wake conditions in other animals, including humans. This is because the circadian clocks are fundamentally similar. Drosophila circadian rhythm was discovered in 1935 by German zoologists, Hans Kalmus and Erwin Bünning. American biologist Colin S. Pittendrigh provided an important experiment in 1954, which established that circadian rhythm is driven by a biological clock. The genetics was first understood in 1971, when Seymour Benzer and Ronald J. Konopka reported that mutation in specific genes changes or stops the circadian behaviour. They discovered the gene called period (per), mutations of which alter the circadian rhythm. It was the first gene known to control behaviour. After a decade, Konopka, Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered novel genes including timeless (tim), Clock (Clk), cycle (cyc), cry. These genes and their product proteins play a key role in the circadian clock. The research conducted in Benzer's lab is narrated in Time, Love, Memory by Jonathan Weiner. For their contributions, Hall, Rosbash and Young received the Nobel Prize in Physiology or Medicine in 2017. History During the process of eclosion by which an adult fly emerges from the pupa, Drosophila exhibits regular locomotor activity (by vibration) that occurs during 8-10 hours intervals starting just before dawn. The existence of this circadian rhythm was independently discovered in D. melanogaster in 1935 by two German zoologists, Hans Kalmus at the Zoological Institute of the German University in Prague (now Charles University), and Erwin Bünning at the Botanical Institute of the University of Jena. Kalmus discovered in 1938 that the brain area is responsible for the circadian activity. Kalmus and Bünning were of the opinion that temperature was the main factor. But it was soon realized that even in different temperature, the circadian rhythm could be unchanged. In 1954, Colin S. Pittendrigh at the Princeton University