samhill wrote:As above if you can use another entry way for awhile they will be gone(I believe), I have had quite a few empty nest blown down in the winter & none showed any sign of hornets or wasps so I'm guessing they head out before winter. They do however seem to get more aggressive & easily aggravated toward the end of the season & that may be why you hadn't noticed them until now.
Actually, the cold weather kills them off. They don't cluster up and eat stored food like honey bees do. They are very active this time of year because of several factors. There are hundreds (thousands?) more of them per hive at this time of their life cycle than there was when the hive started to populate in the spring. There's more of them to to forage and therefore you see them more often. They're always aggressive, your chances are better (or worse

) of meeting up with one near their defensive zone - near their hive.
The hive at this time of the year is preparing for next year only none of them that are flyin now will make it thru the winter. Right, none of them. Deep in the hive are a couple of cells where a pupating queen and a few drones will wait until the spring weather rouses them. The large ones you see in the spring are these fellows. The mated queen starts out on her own. She has to build the start of the hive, lay the eggs, tend, forage and feed the larvae until they pupate and hatch. Now she has a few to help her. As cycle times repeat, the queen can become an egg laying machine with a few hundred (and then a few thousand more ?) to tend the larvae. Compound that cycle out to the end of summer, namely now, and you'll see the big hives and larger numbers of foragers making round trips.
I try to leave them alone if they don't build somewhere that makes it unsafe for people. They eat a tremendous amount of insects. They'll be dying off soon after the first frost. At least the ones that are flying now

It will start all over again in the spring.