I don't know what happened. They were fine just days ago, coming out in groups for orientation flights, and zooming off for water and early pollen or propolis.
But I did notice their doorway seemed really dirty. They usually keep it pretty clean.
Yesterday the Sergeant wondered why there wasn't much activity, despite the warm weather. Just a very few bees coming and going.
I opened up the window today.
Looks like nobody's home.
We'll open the hive itself in a day or two and see what we can see. It's very sad.