What is the sign that snakes appear on ancestral graves in the twelfth lunar month?

There are snakes in the ancestral graves.

The ancestral grave is called a ghost house. Traditionally, the Yin House is regarded as a treasure trove of geomantic omen, known as the "land of living dragons", which can bless the younger generation and developed descendants.

The "land of lively dragons" is surrounded by auspicious clouds all year round. If the ancestors happened to be in "Living Longkou", then the descendants would be great.