There's a significant downside to congregating (e.g.) solitary bees - they can get cleaned out by predators. We had every tube in a 30-tube hotel opened and emp

There's a significant downside to congregating (e.g.) solitary bees - they can get cleaned out by predators. We had every tube in a 30-tube hotel opened and emptied over a weekend by some kind of parasitoid wasp. Now we leave old flower stalks up over the winter.