Abstract: This review deals with the progress in the molecular study on the biologicalclocks in insects. Biological clocks represent a type of cellular regulation common to most eukaryotes. They are disturbed by certain mutations in insects. The genesdefined by certain of these mutations in Drosophila have been isolated. The mostimportant clock gene period has been studied in detail, including its structure,expression, regulation, etc. These investigations are revealing the molecular nature of biological clocks.

Key words: nsect molecular biology, biological clock genes