Bald faced hornet nests will appear in bushes, trees, and attach to the exterior of buildings.
The natural habitat of a European hornet is a hollow tree, however they frequently invade buildings and may build between walls, in attic spaces, or between insulation and ceilings. When their nests occur adjacent to sheet rock, they may chew through the sheet rock. Their nests have a putrid odor.
Aerial yellow jackets are colored very similarly to a normal yellow jacket, however their nests are usually in trees and bushes rather than concealed spaces. Occasionally they will enter a soffit and attach a nest underneath the roof. These insects not only aggressively sting, but can shoot venom at your eyes.
Aerial Yellow Jacket
Hornet nests are constructed of a paper-like material and contain a series of paper brood combs which are covered with a paper envelope and usually have one entrance hole. Most species have exposed exterior nests and can be very aggressive especially late in the summer. Nests are started in the spring by a single individual queen and grow exponentially later in the season.