The Japanese hornet, Vespa mandarinia, is recognized as the world’s largest hornet. This insect is commonly found across temperate and tropical regions of East Asia, South Asia, mainland Southeast Asia, and parts of the Russian Far East. It typically inhabits low mountains and forested areas, often constructing its nests underground in spaces like rodent tunnels or near decaying tree roots.
Understanding the Threat
Its body can measure up to 45 millimeters in length with a wingspan of approximately 75 millimeters, and it is equipped with a stinger about 6 millimeters long. The hornet’s potent venom includes neurotoxins and cytotoxins, which can affect bodily systems.
These hornets can sting multiple times, and while a single sting is painful, a large number of stings can be serious even for individuals without allergies. It is estimated that approximately 100 stings could be a severe dose for a 50 kg person. In Japan, these hornets are associated with 40 to 50 fatalities annually.
Individuals with allergic sensitivities face an elevated risk from stings. Anaphylaxis, a severe allergic reaction, can manifest with widespread hives, swelling of the face, throat, or tongue, difficulty breathing, wheezing, dizziness, or a rapid pulse. Such reactions can progress rapidly to shock or cardiac arrest. A high number of stings can potentially lead to kidney failure or other organ complications.
Responding to a Sting
If a Japanese hornet sting occurs, calmly move away from the area to avoid further stings. The sting site should be thoroughly cleaned with soap and water to minimize the risk of infection. Applying a cold compress or ice pack to the affected area can help reduce swelling and pain. Elevating the stung limb can also help manage swelling.
Unlike honey bees, Japanese hornets do not leave their stingers embedded, so there is no need to attempt stinger removal. Mild symptoms typically include localized pain, redness, swelling, warmth, and itching at the sting site. These local reactions usually subside within a few hours to a day.
It is important to seek immediate medical assistance if signs of a severe allergic reaction develop. These signs include hives that spread beyond the sting, swelling of the face, lips, or throat, difficulty breathing, wheezing, dizziness, or a rapid pulse. If an epinephrine auto-injector is available and the individual is trained in its use, it should be administered immediately, followed by a call to emergency services.
Preventing Encounters
Japanese hornets can establish nests in tree hollows or in urban areas with sufficient green spaces. Queens typically emerge in late March or early April to begin establishing new colonies.
These hornets generally sting when they perceive a threat to themselves or their colony. Approaching a nest, often within a 10-foot perimeter, can provoke an attack. If a hornet is nearby, avoid sudden movements; if one lands on you, gently brush it off and move away calmly.
To prevent encounters, wear protective clothing when in areas where hornets might be present. Avoiding the disturbance of known nests is important, and professional assistance should be sought for nest removal. When consuming food or drinks outdoors, caution is recommended, as hornets are attracted to sugary substances and other insects. Maintaining a tidy property by managing food waste, removing standing water, and trimming trees and debris can help deter hornets from nesting nearby. Sealing small openings in structures can also help prevent them from entering buildings.