Update

This evening after work, I refilled the syrup feeder, cleaned out a pile of chewed wax and beetle larvae (Audrey has developed a taste for shb grubs and now attends every hive inspection), and took a few pictures. There are a lot of really active, hungryhungryhungry, light gold & black striped bees, drinking syrup faster than this hive ever has, even when they were 3,000 strong and new to the neighborhood. I'm no longer seeing the black bees. Whoever these bees are, they are eating everything in sight. Not aggressive, but very busy.
I saw--but wasn't fast enough to squish--a wax moth. It was clunky looking but fast, and kind of booger colored (not unlike its unappealing offspring). Also, a bumble bee dropped in to see what was happening in the hive. I took some pictures of all the activity. In one photo, after viewing it enlarged on the monitor, I saw a bee with a particularly majestic behind. I'm thrilled to think I have finally seen the queen--posted the pic a couple places to elicit some expert opinions.
The bees seem healthy and hearty--just incredibly hungry. I will have to put up a lot of sugar syrup for the housesitters to feed while we're away at the end of the month.
I keep forgetting to mention--for the last two weeks, I've been adding roughly 1 tbsp celtic sea salt per gallon of syrup, for the minerals. The bees seem to like it.