The silk moth is still alone - no more have emerged yet. Yesterday I cut off the stained bit of the cocoon, and emptied out the contents :-
Lovely colour inside the cocoon.
and this is what was inside - the old skin, plus, I think the other bit is the old face from the silkworm. They shed their faces as well as their skins.
Correction : it was the whole worm skin, all squashed up.