We had - for the first time ever - two nests of what we finally identified as European hornets.  They are HUGE!!!  They are attracted to light, so would be crawling on my screens of my living room in the evenings.  Very disturbing.  This not only killed them, but I think we have also got rid of every moth and mosquito in the neighborhood.  We would find piles of bugs on the floor of the porch each morning.  I'm a very happy camper!