The term “black hornet” usually refers to a large, imposing insect, but its identity is often misconstrued. True hornets belong to the genus Vespa. The insect most people encounter that fits this description is the Bald-faced Hornet (Dolichovespula maculata), which is technically a species of aerial yellowjacket wasp. This wasp is known for its distinctive coloration and highly defensive nature, leading to its reputation for aggression.
Identifying the “Black Hornet”
The insect commonly called the “black hornet” is the Bald-faced Hornet (Dolichovespula maculata), a member of the wasp family, not a true hornet. These social insects are easily recognizable by their striking black and white or ivory coloration, unlike the black and yellow of typical yellowjackets. The species name comes from the ivory-white markings on the front of its head, giving it a “bald face” appearance against its dark body.
Worker Bald-faced Hornets measure between 12 and 15 millimeters in length, with queens reaching up to 20 millimeters. Their bodies are predominantly black with characteristic white bands located near the tip of the abdomen and on the thorax.
Other large, dark-colored wasps, such as Mud Daubers and Cicada Killers, are often confused with the Bald-faced Hornet. Mud Daubers are solitary wasps recognized by their slender waist and tubular mud nests. Cicada Killers are also solitary, nest in the ground, and have black and yellow or orange markings, reaching up to 40 millimeters. The Bald-faced Hornet’s social nature and aerial nest construction distinguish it from these less-defensive solitary species.
Understanding Aggressive Behavior
The Bald-faced Hornet’s reputation for aggression is due to its defensive behavior aimed at protecting the colony. These wasps are non-aggressive when foraging away from the nest, focusing on hunting insects and collecting nectar. Workers become highly agitated and attack when they perceive a direct threat, especially during late summer and early fall when the colony population peaks.
Aggression is typically triggered by disturbances within a close perimeter, often a 3 to 5-foot radius of the nest entrance. Sudden movement, vibration, or physical contact with the nest initiates a rapid, coordinated defense. When disturbed, workers swarm out and fly directly toward the perceived threat.
Bald-faced Hornets possess a smooth stinger, allowing them to sting repeatedly without losing it, unlike honeybees. When a hornet stings or is crushed, it releases an alarm pheromone. This chemical signal alerts other colony members to join the attack, rapidly escalating the defensive response and potentially resulting in a swarm defending the nest.
Nest Location and Structure
The Bald-faced Hornet constructs a distinctive aerial nest made from a paper-like material that hangs from a stable structure. Workers create this material by chewing wood fibers and mixing them with saliva, spreading the resulting pulp into gray, multi-layered, enclosed structures. These nests are typically spherical or football-shaped, often reaching up to 24 inches in length by the end of the season.
Common locations include high tree branches, dense shrubs, utility poles, or under the eaves of buildings and roof overhangs. The nest is accessed through a single opening, usually located near the bottom. The colony population can number between 100 and 400 workers in a single season. Since these colonies are annual, only the mated queen survives the winter by hibernating, while the workers and the old nest die off.
Safe Interaction and Management
The most effective way to avoid being stung by a Bald-faced Hornet is to be aware of their presence and maintain distance from their nest. If a hornet is encountered while it is foraging, the best approach is to remain calm and move away slowly, as swatting or sudden movements are likely to provoke a defensive reaction. Wearing shoes outside can also prevent accidental stings from a hornet that may have landed on the ground.
For nests located far from human activity, such as high in a distant tree, the most passive and safest management strategy is often to leave it alone. The colony will naturally die out with the first hard frost, and the nest will not be reoccupied. However, if a nest is located close to a home, deck, walkway, or other high-traffic area, it presents an unacceptable safety risk due to the insect’s aggressive defense.
In situations where a nest must be removed, it is strongly recommended to contact a licensed pest control professional. Attempting a do-it-yourself removal of a Bald-faced Hornet nest is highly dangerous, as the aggressive swarm response can lead to multiple stings and potential allergic reactions. If stung, basic first aid involves cleaning the site and applying a cold compress to reduce swelling, but individuals who experience severe symptoms like difficulty breathing or swelling of the throat require immediate medical attention.