San Pedro Atocpan was celebrating the monarch butterfly for the Day of the Dead.
The church incorporated the beliefs/ceremonies of the indigenous peoples into Catholic beliefs.

One of the 12 original settlements of Milpa Alta. It’s believed to have
been settled between the years of 120 and 140 CE. The people are said to
be the descendants of one of seven Nahuatlacan tribes who lived on the
southern banks of the lake.