Biological rhythms, such as the sleep-wake cycle or circadian clock, are an intriguing aspect of biology. The regulation of daily rhythmicity has long been a mystery, up until the mid-1980's when a key gene in the fruitfly, Drosophila melanogaster, was molecularly identified. Genetic and molecular chronobiology of Drosophila has been a driving force in this field of inquiry ever since. This book describes and evaluates all of the studies of this sort, discussing the manner by which these investigations have spread out in various directions of rhythmic biology, including genetic and molecular approaches used on other insect species. * Discusses rhythm genetics in insects, from early investigations to current state-of-the-art * Presents all relevant mutants and genes * Highlights the mystery of the "clock mechanism" in full detail including the remaining puzzles to be solved.