Spatial distributions of our catalogued star clusters. The coordinate (0, 0) represents the centre of M31 (green ‘Y’; RA = 00^h42^m44^s.30, Dec = +41° 16′09^″.0). The green ellipse represents the optical disk of M31, for which we adopt a major axis length of 1.59°, a disk inclination angle of 78°, and a major axis position angle of 38°. Top panel: global spatial distribution of all the 346 sample clusters. Red and blue circles are respectively young and old clusters. Middle and bottom panels: spatial distributions of young and old clusters, respectively, in the zoomed-in areas of the M31 disk. The colours represent the cluster metallicities.