Do Asian Lady Beetles Bite?

Most of what this hub corrects is an overblown fear about a harmless insect. This question is the exception, and it deserves a straight answer instead of a reflexive debunking. Koch's standard peer-reviewed review of the species' biology states plainly that Harmonia axyridis "has been reported to bite humans," consistent with its functional chewing mandibles (Koch 2003, Journal of Insect Science). University of Minnesota Extension is specific about the circumstances: individuals searching skin for moisture or salt "can bite hard enough to break human skin, causing minor, short-lived discomfort." UNH Cooperative Extension describes the sensation as roughly equivalent to a pinprick — not a puncture wound, not venom, and gone quickly, but a genuine bite rather than a myth. A beetle simply crawling on skin isn't biting; the nip happens when one is pressed against skin or trapped against it, which is also often the moment a disturbed beetle reflex-bleeds its defensive fluid at the same time, adding a foul smell and a yellow stain to the encounter. In New Hampshire the encounters cluster in fall, when UNH Cooperative Extension reports the beetles are most numerous on the sunny side of buildings on mild days from mid-September through early November and begin working their way indoors — which is when a household is most likely to feel one of these nips at all.

The bite itself is minor. What makes this beetle a genuine, documented health consideration is the allergen. Nakazawa et al. purified two proteins from Harmonia axyridis, Har a 1 (about 10 kDa) and Har a 2 (about 55 kDa), and found they "bound IgE antibody in 65% and 75% of the sera, respectively," from patients living in infested homes (Nakazawa et al. 2007, Journal of Allergy and Clinical Immunology). A clinical review in Allergy and Asthma Proceedings confirms the beetle has become a recognized seasonal indoor allergen capable of producing rhinoconjunctivitis, asthma, and skin reactions in sensitized people (Goetz 2008). That allergen risk, not the nip, is the more consequential half of this page's answer, and it is covered in full depth — including who's most at risk and what symptoms look like — on this hub's page about whether they can cause allergies. None of this makes the beetle dangerous in the venomous or disease-carrying sense: it is a real nip plus a real, but bounded and well-characterized, allergen.