The Asian lady beetle, Harmonia axyridis, is a common insect often mistaken for native ladybugs. Many people wonder about their interactions with humans, particularly if these beetles are capable of biting. Understanding this insect’s characteristics and behaviors helps clarify why this concern is so prevalent.
Understanding Asian Beetles
Asian lady beetles are native to East Asia and were intentionally introduced to North America and Europe for biological control, managing aphid populations. They are now widespread.
These beetles are quite variable in appearance, with colors ranging from yellow to orange or red, and sometimes even black, often displaying varying numbers of black spots or no spots. A distinguishing feature is the presence of an ‘M’ or ‘W’ shaped black marking on the white area directly behind their head, known as the pronotum. They are dome-shaped and about 1/4 inch (6 mm) long.
Do They Nip Humans?
Asian lady beetles can “nip” or “pinch” humans, though it is not a true bite intended for feeding like a mosquito’s. This sensation is usually described as a minor, momentary pinch that causes short-lived discomfort. They typically do this as a defensive mechanism when they feel threatened, are trapped against the skin, or are seeking moisture, especially in dry conditions when food sources like aphids are scarce.
When disturbed, Asian lady beetles also have a defense mechanism called “reflex bleeding,” where they excrete a foul-smelling, yellowish fluid from their leg joints. This fluid can stain surfaces.
Reactions to an Asian Beetle Nip
For most individuals, a nip from an Asian lady beetle results in no significant reaction or a very mild, temporary irritation. This might appear as a small red mark or slight itch that quickly subsides. If a nip causes concern, cleaning the area with soap and water is a sensible first-aid step.
In some cases, sensitive individuals may experience allergic reactions, though this is uncommon. Symptoms of an allergic reaction can include more significant skin irritation, hives, itchy eyes, sneezing, or a runny nose. In rare instances, prolonged exposure to large infestations has been associated with respiratory symptoms or even asthma attacks. If an allergic reaction is suspected or symptoms persist, seek medical attention.
Preventing Encounters
To reduce encounters with Asian lady beetles, especially indoors, several measures can be taken. Sealing cracks and openings around windows, doors, and utility entry points with caulk or other sealants can prevent them from entering. Repairing damaged window screens is also important to block access.
If beetles do enter a home, using a vacuum cleaner is an effective way to remove them without crushing them. Crushing them can trigger the release of their foul-smelling, staining fluid. Outdoor encounters are less likely to result in nips unless the beetle feels threatened.