The term “black hornet” often evokes concern, as many people assume large, dark-colored flying insects are highly dangerous. However, the insects commonly referred to as “black hornets” encompass several distinct species, each with unique behaviors and varying levels of threat. Understanding these differences is important for accurately assessing risk. This article will clarify the identities of these insects and explain when and why they might exhibit defensive behaviors.
Understanding “Black Hornets”: Identifying Common Species
The term “black hornet” often refers to several large, dark-bodied insects, not a single species. Among the most commonly encountered in North America is the Bald-faced Hornet (Dolichovespula maculata), a type of yellowjacket. These insects are characterized by their mostly black bodies with white or ivory markings on their face and the end of their abdomen. Bald-faced hornets construct large, gray, football-shaped paper nests, suspended in trees, shrubs, or on buildings, which can grow up to 24 inches long.
Another insect frequently identified as a “black hornet” is the European Hornet (Vespa crabro), the only true hornet species established in North America. European hornets measure between 1/2 to 1.4 inches, with brownish bodies, dull orange stripes, and a pale face. Unlike bald-faced hornets, they build their paper nests in concealed locations such as hollow trees, wall voids, or attics.
Cicada Killers (Sphecius speciosus) are up to 2 inches long, with black bodies, yellow markings, and amber-tinted wings. These are solitary wasps that dig individual burrows in the ground, often in sandy or loose soil. Mud Daubers are also solitary wasps, recognized by their slender bodies, often black, yellow, or metallic blue, and a very thin “thread-waist.” They construct tube-like nests from mud, located under eaves or in sheds.
Finally, the Great Black Wasp (Sphex pensylvanicus) is entirely black with smoky wings, measuring between 0.8 to 1.4 inches. Like cicada killers and mud daubers, these are solitary ground-nesting wasps that dig burrows in the soil. The diverse appearances and nesting habits of these insects underscore the importance of accurate identification.
Assessing Aggression: When and Why Hornets Attack
The aggression levels of these insects vary significantly, largely depending on whether they are social or solitary species. Social insects, such as Bald-faced Hornets and European Hornets, exhibit strong defensive behaviors, particularly when their nests are disturbed. Bald-faced Hornets are aggressive and defend their large paper nests, pursuing threats and stinging repeatedly. European Hornets, while less aggressive when foraging, will protect their concealed nests if threatened, and can sting multiple times.
When a social wasp or hornet perceives a threat to its colony, it can release chemical signals known as alarm pheromones. These pheromones, often found in their venom sacs, alert other members of the colony to the danger. This chemical communication can lead to a coordinated attack, where numerous individuals swarm and sting the intruder. Crushing a social wasp can release these pheromones, intensifying the defensive response of nearby colony members.
In contrast, solitary wasps like Cicada Killers, Mud Daubers, and Great Black Wasps are less aggressive towards humans. Cicada Killers primarily use their sting to paralyze prey, such as cicadas, for their larvae. They rarely sting humans unless directly handled or stepped upon; male cicada killers lack a stinger entirely. Mud Daubers and Great Black Wasps are also non-aggressive; stings from these solitary species are uncommon and only occur if they are mishandled or their individual nest is directly threatened. Their focus remains on nest building and provisioning, not on defending a large colony.
Preventing Stings and Managing Encounters
Minimizing the likelihood of stings involves both prevention and appropriate responses during encounters. To prevent attracting these insects, keep outdoor eating areas clean, covering food and sugary drinks, and promptly disposing of fallen fruit. Securely sealed trash cans also help reduce attractants. Avoiding strong perfumes, colognes, and floral-scented products can also lessen attraction.
Wearing light-colored, smooth-textured clothing that covers exposed skin, such as long sleeves and pants, can deter them, as dark or brightly colored garments may attract attention. Regularly inspecting and maintaining your property by trimming vegetation and sealing cracks in structures can reduce potential nesting sites. If a nest is discovered, never attempt to remove it yourself; contact a pest control professional.
If a “black hornet” approaches, remaining calm and moving away slowly is best, as sudden movements or swatting can provoke an attack. If chased, running in a straight line to a sheltered location like a building or vehicle is the most effective strategy. In the event of a sting, wash the affected area with soap and water and apply a cold compress to reduce pain and swelling. Over-the-counter pain relievers and antihistamines can help manage discomfort.
A severe allergic reaction, or anaphylaxis, requires immediate medical attention. Symptoms include widespread hives, facial or throat swelling, breathing difficulties, dizziness, or a sudden drop in blood pressure. If an individual has a prescribed epinephrine auto-injector, it should be administered without delay, and emergency services contacted immediately.