  Sunspot groups observed by Royal Greenwich Observatory/US Air Force/NOAA from
May 1874 to November 2008 and the Carte Synoptique solar filaments from March
1919 to December 1989 are used to investigate the relative phase shift of the
paired wings of butterfly diagrams of sunspot and filament activities.
Latitudinal migration of sunspot groups (or filaments) does asynchronously
occur in the northern and southern hemispheres, and there is a relative phase
shift between the paired wings of their butterfly diagrams in a cycle, making
the paired wings spatially asymmetrical on the solar equator. It is inferred
that hemispherical solar activity strength should evolve in a similar way
within the paired wings of a butterfly diagram in a cycle, making the paired
wings just and only keep the phase relationship between the northern and
southern hemispherical solar activity strengths, but a relative phase shift
between the paired wings of a butterfly diagram should bring about an almost
same relative phase shift of hemispheric solar activity strength.
