These pests build large nest colonies, much larger than their paper wasp relatives, consisting of several combs surrounded by paper envelopes and resemble a paper-mache ball. Most other yellow jackets build nests underground or within enclosed sites such as wall voids, attics and inside hollow logs.
Baldfaced hornets, however, generally build their nests in trees and shrubs or on buildings. Nests are generally build around April/May, are occupied until late fall, and are not re-used the next season.
The population in mature colonies can be quite large, ranging from 200 to 700 adults. Due to their large colony size and defensive nature, baldfaced hornets are more aggressive than paper wasps.
These hornets have effective means of defending their colonies. They often have “guards” at their nest entrances, and the colony can easily be disturbed by rapid movement and vibrations near the nest. For this reason, a human will almost certainly be stung if a lawn mower or trimmer is used near a bald faced hornet nest.
A nest located in a high traffic area such as along a sidewalk or near a doorway may need attention, but nests away from human activity should be left undisturbed as baldfaced hornets are beneficial insects that feed on other insects like blow flies and filth flies.
Bald faced hornet colonies usually last until late fall in the Tri-State area, outlasting paper wasps, hence have more opportunity for unpleasant interaction with humans and thus have a nastier reputation than even paper wasps.