Analysis of an 18-year combined synoptic monitoring catalog shows the existence of three non-Io-related source regions on Jupiter, with centroids being located near but not exactly at the centroids of the three well-known Io-controlled sources. Both Io-controlled and non-Io-controlled sources show variation of occurrence probability with declination of earth (DE) but with distinctly different patterns: the occurrence probability of Io sources peaks near DE=0¿, while that of non-Io sources show a much greater range of variation and peaks near DE=2¿. Both the Io and the non-Io components of the second and third ('main' and 'late') sources show a positive correlation of centroid longitude with DE, although the non-Io source variations are linear, while the Io source variations are curved. Io sources 1 and 3 show clear evidence of variation in the Io coordinate of their upper boundary with DE. When correction for this effect is made, extremely sharp gradients in occurrence probability are produced, leading to a further distinction between Io and non-Io sources on the basis of the significantly sharper directivity gradients in the Io sources.