I only know what I am told by the locals, of which, I am not.... the fall line is an area in Central Georgia where the central plain ends and the hills and later mountains begin....there is a change in the type of earth which has to do with gnat reproduction.... , so that same area, they call it the gnat line.... if you are below it, you are plagued with gnats.... Where I am located, (South Macon) it seems to vacillate a bit so sometimes it is gnats and sometimes it is not... but when it is.... let me tell you, there are a lot of bugs in the air in Ga.I'm already itching after reading this thread, and that link... so I might as well ask, what is this "gnat line"? Does it relate to different forest type? Of something else?