Mark discovered this Peacock in a cave at Portland on 3/08/18 and tells us:
There were 6 all suspended from a tunnel ceiling on Portland. The white sack is apparently a spider’s egg sack that likes to inhabit caves in Europe.
The camouflage is amazing when Peacock butterflies roost in the dark nooks and crannies of caves.
It is possible that during periods of intense heat, when butterflies can become dehydrated and die, these Peacocks have entered a state of diapause, a condition in which their metabolism is lowered to a level where flying, feeding and breeding is suspended.