Yellow jackets, a common group of social wasps (Vespula), are frequently encountered nuisance insects known for their aggressive defense of their nests. They are often found entering and exiting holes in the ground. Understanding their nesting behavior is key to safely managing their presence.
The Truth About Yellow Jacket Excavation
Yellow jackets, specifically ground-nesting Vespula species, do not possess the specialized structures required for actively excavating tunnels in soil. They cannot bore into compacted earth. The queen, who initiates the colony in the spring, relies entirely on finding a pre-existing void or cavity to establish her nest.
The wasps utilize natural depressions, such as voids left by tree roots, or spaces created by human structures like retaining walls or sidewalks. Most commonly, they appropriate abandoned burrows from small mammals, such as mice, voles, or gophers, which provide an immediate, protected space. The queen then begins constructing the initial paper cells within this existing chamber.
Location and Structure of Ground Nests
Once a suitable underground cavity is located, the queen builds the nest using carton, a paper material created by chewing weathered wood fibers and mixing them with saliva. The nest is a layered, enclosed structure built within the chamber, separate from the surrounding soil.
The structure consists of multiple parallel layers of hexagonal comb, all encased in a protective paper envelope. This contrasts with the single-layer comb of paper wasps. As the colony grows throughout the summer, worker wasps expand the paper nest, sometimes moving soil and debris to enlarge the subterranean chamber. By late summer, a colony can contain thousands of workers, often housing up to 5,000 in species like the Eastern yellow jacket (Vespula maculifrons). The average depth of these nests is approximately 28 centimeters below the surface.
Identifying and Dealing with Ground Activity
The presence of a ground nest is typically identified by a single, small entrance hole with a constant stream of wasps flying in and out. This steady, directional traffic, sometimes called a “bee-line,” distinguishes a yellow jacket nest from the more sporadic activity of solitary ground-nesting bees or ants. The entrance is generally clean and free of the excavated soil mound often found near ant or rodent holes, as the wasps disperse the debris they remove.
If you locate this activity, maintaining distance is the safest immediate action, as ground nests are easily disturbed by vibrations from foot traffic or lawn mowing. Yellow jackets are intensely defensive of their colony and will aggressively swarm to sting a perceived threat. For removal, it is recommended to contact a pest control professional, as treating a ground nest is dangerous due to the large number of defensive wasps emerging from the hidden entrance.