The presence of stinging insects around your home can be alarming, especially when they are large and boldly marked. The insect commonly known as the bald-faced hornet is actually a species of aerial yellowjacket, Dolichovespula maculata, not a true hornet. Understanding what draws these social wasps into human-occupied areas is the first step in prevention, as they are drawn to properties by the nutritional requirements of their colony and the availability of suitable nesting materials and sheltered locations.
Identifying the Bald-Faced Hornet
These wasps are distinct from other yellowjackets. The bald-faced hornet is mostly black with striking ivory-white markings, particularly on its face, which gives the insect its common name. An adult worker typically measures between 13 and 20 millimeters in length. Unlike honey bees, these yellowjackets have a smooth stinger, allowing them to sting repeatedly if their nest is threatened. The colony’s population peaks in late summer and early fall, which is when most people notice their increased foraging activity around homes.
Food-Based Attractants
The foraging behavior of the bald-faced hornet is governed by the shifting dietary needs of its colony throughout the season. In the spring and early summer, the workers focus on gathering protein to feed the developing larvae. This protein is sourced from soft-bodied insects, such as flies, caterpillars, and spiders, which the workers hunt and chew into a digestible paste. These predatory activities help control populations of other pest insects in the area.
As the summer progresses and the larval population declines, the food requirements of the colony change. Adult workers shift their focus to carbohydrates for their own energy, as they no longer need to find as much protein for the young. They are attracted to natural sugar sources, including flower nectar, tree sap, and the juices of overripe or fallen fruit. This search for sugars is why they become more noticeable and sometimes aggressive around human activities in the late summer and fall.
Structural and Nesting Preferences
Beyond their food requirements, the bald-faced hornet seeks locations for building its characteristic nest. The wasps create a specialized paper pulp by chewing weathered wood fibers and mixing them with their saliva. They actively seek out sources of raw cellulose, such as old fence posts, unpainted wooden siding, or weathered decks, to construct their paper nests.
The preferred nesting sites offer protection and security. These aerial nests are often suspended high in the branches of trees or dense shrubs. However, they will also readily utilize sheltered spots on human structures, including under the eaves of a roof, beneath porch overhangs, or inside attic spaces. A single nest can grow to be the size of a basketball, housing hundreds of workers before the colony naturally dies off in the cold weather.
Common Household Attractants
Human activity often provides the food and material sources these wasps seek, drawing them close to homes. Uncovered outdoor trash cans and compost piles are attractants, as the decaying organic matter mimics the protein and sugars they find in nature. Spilled sugary beverages, like soda or juice left open during a picnic, are irresistible carbohydrate sources.
Pet food bowls left outside can offer a protein meal. Older, unpainted wooden structures on a property, such as sheds or playhouses, represent a readily available source of construction material for the nest. The presence of water sources, including birdbaths or small pools, also attracts foraging workers who need water to mix the wood pulp for construction.