The wasp pictured is indeed a European Hornet, and the nest pictured is that of a Baldfaced Hornet. Northern Giant Hornets (formerly named Asian Giant Hornets and misleadingly and sensationally named Murder Hornets by the media) are larger, have a different body coloration pattern, and do not occur in the U.S. outside of those isolated detections a few years ago in Washington State.

European Hornets are non-native but have been in North American for over a century and are well-established. Their nests resemble that of the Baldfaced Hornet but they are not constructed out in the open; they are hidden inside tree hollows or other sheltered voids, occasionally (but not often) inside wall voids, though Yellowjacket wasps are more typically the culprit in that case. All social wasps (Yellowjackets, hornets, paper wasps) feed on sources of sugary liquids (flower nectar, oozing tree sap, fallen fruits, etc.) as adults and hunt other insects as prey for their young back in the nest. They do not seek-out confrontations with people but will defend a nest if they perceive a threat. Individuals also might sting if they feel threatened as they go about foraging, such as if they are swatted. (Or if a dog nuzzled one smelling it or trying to catch it in their mouth. Otherwise, the dogs are probably going to be ignored.)

Social wasp nests are not re-used from year to year. By autumn, nest populations are at their largest since they have been building all summer, but with frosts and the end of the season, all members of the nest will die out except for a handful of new "queens" (young females that mate and will become the founders of next year's nests). It might not be the first frost that kills them all, but they won't tolerate many freezes. These queens leave the nest of their birth, mate, and find a sheltered area in which to overwinter alone. Usually this is under loose tree bark, under a fallen log, or a similar spot, but occasionally a female finds an access point into a home and might wind-up inside by accident because it's appealingly warm and dark compared to outside. (We often receive inquiries about hornet queens found inside in spring, when they have roused and are ready to leave and explore; they can't find their way back outside in that situation and sometimes expire before they are found.)

European Hornets have the unusual trait of flying both day and night, and like many night-flying insects, can be attracted to light sources like porch lights and flashlights. If they gather near a doorway when lights are left on all night, they might wind-up inside when the door is opened or if the weather-stripping, torn window screening, or another access point is available to them. Therefore, finding the odd wasp indoors from time to time probably doesn't indicate they are nesting in a wall or attic or even near the home, though regular incursions could be investigated by a pest control professional just in case. A nest which can be avoided until later in autumn does not need treatment since the wasps are about to die out or abandon the nest, but if walking too close to an active nest can't be avoided and the wasps are stinging, then treatment might be warranted for safety. If the wasps have been leaving people alone to date, it's likely they can continue to coexist without conflict for a few more weeks without the need for pesticide application. Weather and wildlife disintegrate old nests (they are essentially made of paper), so it's unlikely any nest seen now in a tree is from a prior year.

Miri