There is a very old garden umbrella at a corner of our patio. Nothing special to us. However, although our patio offers different possible habitats (shader, more humid, sunnier, etc.) it seems to be special to butterflies that congregate only there.
The Garden Commodore or Garden Inspector (Precis archesia) a common butterfly exhibits aggregation behaviour, believed to obey to seasonal changes and survival. They tend to overwinter in large groups during the cooler winter months (April to August), apparently to conserve heat (I am not sure how they do this). In our case, the numbers perched on the umbrella vary between 6 and 12 and they are the dry season type.
They like enclosed, dark, or shielded environments to cluster together and they are seen aggregating inside houses behind curtains or tucked away inside garden tool sheds.
Dry season form.
The temperature they experience during they pupal stage determines which colour pattern and wing shape the butterflies will have. The colours are so different as to make you think that they are different species.
The wet season variation is shown below. The picture credit is of Diego Delso, delso.photo, License CC BY-S
A Bushsnob in Africa 
Where I live we also refer to our seasons as Wet and Dry. We are currently in the Dry season, which produces flowers, so lots of butterflies. Our rain is tropical so Butterflies would be beaten to the ground by heavy rain.
LikeLike