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Pest Management Priducts Division of CSPA
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Ladybugs, in general, actively prey on aphids and other soft-bodied insect plant pests. Both adults and immature multi-colored Asian lady beetles kill significant numbers on these plant pests, especially aphids. Additionally, the multi-colored Asian lady beetle aggressively pursues these plant pests that attack trees; more so than our native ladybugs. In 2000, the soybean aphid, an exotic aphid from China, was discovered feeding on soybean plants. In 2001, the multi-colored Asian lady beetle fed heavily on the soybean aphids and likely saved Michigan soybean farmers millions of dollars in harvest revenues and insecticides that didn't have to be used to control losses to this aphid species.
Multi-colored Asian lady beetles are harmless. They cause no harm to a building or its contents, including people and pets. However, when they show up inside the house by the dozens or hundreds, they usually wear out their welcome.
Some bite, most do not. Sometimes the Asian lady beetles bite skin, but often this stinging sensation is actually caused by small spurs on the beetle's legs pricking skin as they move and evaluate whether or not the skin is a food source. The beetle does not carry disease nor does it have any toxin associated with its mouthparts. In most cases, the pain is short lived. If the bite concerns you, apply antiseptic to the site.
When multi-colored Asian lady beetles are agitated they give off a yellowish fluid that has a faint, foul odor. This is a defensive reaction to ward off predators. It is called "reflex bleeding." The liquid is exuded from its legs and it can stain.
It is possible to have an allergic reaction to the multi-colored Asian lady beetle. Prolonged exposure to infestations has been reported to cause allergic reactions in some humans (Yarbrough et al 1999, mangnan et al. 2002), and repeated exposure to dead lady beetles can cause an allergic reaction in some individuals. Patients have described itchy nose and eyes, sneezing, upper respiratory symptoms, and severe, persistent asthma. Here are some references about research in this area:
Magnan EM; Sanchez H; Luskin AT; Bush RK. 2002. Multicolored Asian lady beetle (Harmonia axyridis) sensitivity. Journal of Allergy and Clinical Immunology, Volume 109, Issue 1, pp 205
(free access to abstract)
Yarbrough, JA MD, Jack L. Armstrong, MD, Michael Z. Blumberg, MD, Amy E. Phillips, BS, Edna McGahee, RN, William K. Dolen, MD. Allergic rhinoconjunctivitis caused by Harmonia axyridis (Asian lady beetle, Japanese lady beetle, or lady bug) Journal of Allergy and Clinical Immunology September 1999, part 1, Volume 104, Number 3, p704 to p 705
i (Paid access only to article).