The insects most commonly found nesting in the ground are not true hornets, but rather Yellowjackets, belonging to the Vespula and Dolichovespula genera. The public often mistakes these aggressive, scavenging wasps for hornets due to their similar appearance and stinging behavior. True hornets belong to the genus Vespa and typically favor nesting in aerial locations, tree hollows, or wall voids rather than subterranean burrows.
Identifying the Primary Ground Nesters
The primary insects that build nests underground are Yellowjackets, including species such as the Eastern Yellowjacket (Vespula maculifrons), the Western Yellowjacket (Vespula pensylvanica), and the German Yellowjacket (Vespula germanica). These wasps are relatively small, averaging about one-half inch in length, with a smooth body and bright yellow and black banding. Unlike bees, Yellowjackets lack dense body hair, and their abdomen tapers sharply to a narrow “wasp waist,” distinguishing them from the fuzzier honeybee.
These species habitually exploit pre-existing cavities for their nests, most often utilizing abandoned rodent burrows, tree root cavities, or natural fissures in the soil. The German Yellowjacket will readily use ground cavities, though it is also known for nesting in wall voids and attics. The European Hornet (Vespa crabro) is a true hornet that nests in North America, but it is much larger, with a reddish-brown and yellow-orange coloration. It generally prefers low, dark cavities like hollow trees or sheds, rarely choosing a true subterranean nest.
Distinguishing Ground Nests from Other Insects
Identifying a Yellowjacket ground nest relies on recognizing the distinct pattern of the entrance and the traffic volume of the insects. The entrance is usually a single, small, often inconspicuous hole in the soil, which may be located under a stone, in a woodpile, or concealed by overgrown grass. Unlike ant or rodent tunnels, there is rarely a large, excavated mound of dirt surrounding the hole, as Yellowjackets utilize an existing space.
The most telling sign is the constant, high volume of insect traffic entering and exiting the single opening, with workers flying in a direct, purposeful line. This activity contrasts with the slower, less aggressive, and sporadic flight of solitary digging wasps or the few, larger bumblebees that might use a similar burrow. Yellowjacket activity is particularly intense during the late summer and early fall as the colony reaches its peak population, which can number in the thousands.
Why Ground Nests Present Unique Dangers
Ground-nesting Yellowjackets pose a heightened risk due to the hidden nature and vulnerability of their colonies. The nest is often located in high-traffic areas such as lawns, flower beds, or trails, making accidental disturbance by lawnmowers, pets, or foot traffic highly probable. When the ground above the nest is vibrated or stepped on, the entire colony is instantly alerted.
Yellowjackets are aggressive, especially when defending their nest. When disturbed, workers are released in a mass defense, with each individual capable of stinging multiple times because their stingers are not barbed like those of a honeybee. This defensive action is compounded by the release of an alarm pheromone, which signals other workers to join the attack, resulting in a painful, overwhelming swarm.
Safe Practices When Encountering a Ground Nest
The most effective practice upon discovering a ground nest is to maintain a significant distance, ideally at least 20 feet, and clearly mark the area to prevent accidental intrusion. Non-intervention is often the safest option if the nest is in a remote or unused location, since the colonies are annual and will naturally die off with the first hard frost of winter. Only the mated queens survive by overwintering elsewhere, and the nest will not be reused the following season.
Attempting do-it-yourself removal is strongly discouraged because actions like pouring water or gasoline into the hole, or blocking the entrance, will likely provoke a mass defensive swarm without eliminating the entire colony. If the nest is in a location that poses a direct threat to people or pets, contacting a professional pest control service is the safest course of action. These professionals possess the necessary protective equipment and targeted application methods to eliminate the colony safely and effectively.