I recently had a camponotus pennsylvanicus queen die on me. She was fine one day, then she started having fits, twitching and was dead in 10 hours. Two days later she was covered in fuzzy fungus.
So, really I have my answer, she got infected and died. We don't always know why they die. Exoskeletons are so inscrutable.
But, also, she started the fits right after I vacuumed. I didn't vacuum her shelf, but I was in the same room running it for a long time. After I found my lasius in a pile, and they slowly spread out over an hour. (but they also needed water so that's hardly conclusive) Other ants didn't notice, but the big carpenter girl was twitching and clearly dieing.
I keep thinking "could it have been the sound?" The vibrations?
So, does running a vacuum freak out ants?