The adult beetles will emerge from the pupae after 3-30 days, depending on environmental conditions LINK.
The pupa is whitish, turning brown with time. It lies about helplessly, wriggling at intervals.
Within one to three weeks it will struggle to rid itself of the old pupal skin to emerge as a beetle LINK.
The newly emerged beetle is whitish with various parts light brown (see video below).
With time the beetle will turn brown, darkening as the days go by.
16th December 2016