I had something related happen last Friday - I came home from a friend's house, where I had been for about 6 hours, and found 6 dead hornets on the floor in my living room, plus two barely alive! Fortunately, none flying around. How did they get in? Where did they get in? Is there a nest in the house? I had to figure this out quickly! After checking just about everywhere, I figured out that the fireplace was the source - despite the damper seeming to close tightly, they must be getting in there. The ash hole was even tighter sealed outside. There was one hornet barely moving in there, so I sprayed it with a natural, but deadly spray, consisting of clove, cinnamon, and several other essential oils; I also sprayed around the damper, and sealed off the fireplace as well as possible, and the next day I looked outside, and they were hovering around the top of the chimney, as if there was a nest there. Still none showing up inside any more, fortunately! So I found local exterminator that a friend had used, and set up an appointment, but they seemed to disappear by the time he got here on Wednesday (I could have gotten a quicker appt., but we know how those extras get charged for emergencies or weekends!). The fellow said that he had never seen anything like this before! The only European hornets he's seen nested in trees, and there are none near my chimney. He said since it was raining that day, maybe some went into the chimney, to escape the rain, but he was just guessing. Since none are hovering there anymore, like the day after, they probably went somewhere else to nest. Hopefully, not nearby! The worst experience I ever had with these kinds of insects was when I hit an underground yellow jackets nest, with a roto tiller! Stung me 23 times! I'm lucky I'm not severely allergic! I watched from a distance, as they went back to their nest holes, and at night I poured some 20% acetic acid down the holes. Never saw another one, though I watch closely for them.
