Chronobiology is the study of timing mechanisms in biological systems as diverse as plants, animals and some micro-organisms. It includes rhythmic phenomena ranging from short period (ultradian) through daily (circadian) to long period (monthly, annual) cycles of behaviour, physiology and biochemistry. In recent years spectacular advances have been made, particularly in the field of circadian rhythms, and hardly a week passes without important papers appearing in the major scientific journals. The third edition of Insect Clocks , like its predecessors, deals with the properties and functions of clock-like processes in one of the planet's most abundant groups of organisms. The first half of the book is concerned with circadian rhythmicity, the second with annual responses such as over-wintering diapause, seasonal morphs and cold hardiness. Insect Clocks puts modern developments in these fields into a secure framework of the 'classical' literature that has defined the subject. The book is directed at active researchers in the field as well as newcomers and scientists working in many other areas of modern biology. It will also serve as a textbook for advanced and less advanced students and should find its way into university libraries wishing to keep abreast of the times.