I am up in Nova Scotia, and almost every year, late in the Summer, they will swarm to the west side of our house. Hundreds of them! I'm here alone through the day, and I merely fold a piece of paper, and gently scoop them into same, and release them inside the house. We both love seeing them through the Winter, crawling around the ceilings and in the kitchen. I never counted the spots, but you have given me something to think about. This Spring, we had some LED pot light replaced in the ceiling, and out of one fell a bunch of deceased "friends". I read already that an Asian strain had been introduced to North America a few year ago. Cheers!

I occationally found them in quite a number too, usually when the weather are too cold or too dry,
I have no clue to the species, but seems from different species all gathering, like ladybugs club congregation.. sorry for the terrible photo