Filament butterfly diagrams constructed from the observations of PM (top) Hα archive compared to those from Mi (bottom). The diagrams show daily mean filament areas within latitudinal strips of 1° as fractions of the area of the entire solar disc. White means no observed filaments, and blue denotes the filament fractional areas that become darker with growing areas up to the saturation level of 2 × 10⁻⁴.