Where Did Asian Beetles Come From?
Multi-colored Asian lady beetles, also known as Harmonia axyridis, are native to Asia and were introduced to the United States in the 1980s as a biological control agent to combat agricultural pests such as aphids and scale insects. However, they quickly became established in North America and are now considered an invasive species in many parts of the continent.
In Iowa and other parts of the Midwest, multi-colored Asian lady beetles are particularly abundant in the fall when they seek shelter in homes and other structures to overwinter. This behavior, known as "massing," is believed to be driven by a combination of factors, including the beetles' natural instinct to seek out warm, protected spaces and the availability of suitable overwintering sites in human-built structures.
Another factor that may contribute to the abundance of multi-colored Asian lady beetles in Iowa is the region's large-scale agricultural operations. The beetles are known to feed on a variety of crops, including soybeans, corn, and fruits, and may be attracted to agricultural areas as a food source.
While multi-colored Asian lady beetles are not harmful to humans, they can be a nuisance when they invade homes in large numbers. Vacuuming or sweeping them up is a common control method, but preventative measures such as sealing cracks and gaps in the home's exterior and using screens on windows and doors can also be effective in reducing their numbers.
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