Watch on Demand



Asian lady beetles a nuisance this time of year

Beetles searching for overwintering sites

Wikimedia Commons/John Elson SOURCE: Wikimedia Commons/John Elson
Asian lady beetles a nuisance this time of year
Beetles searching for overwintering sites

Warm fall days are bringing a relative newcomer to our shores onto the side of your house.

Asian lady beetles were first reported in the United States during the early 1990s and since then, they have been looking for a place to spend winter in your house.


Ladybugs normally are considered beneficial, since they live outdoors and feed on plant pests.

One species of lady beetle, (Harmonia axyridis) can be a nuisance, however, when they fly to buildings in search of overwintering sites and end up indoors.

Once inside, they crawl about on windows, walls, attics, often emitting a noxious odor and yellowish staining fluid before dying.

Asian lady beetles generally do not injure humans and are mainly a nuisance.

Unlike some household pests such as fleas and cockroaches, they do not reproduce indoors and do not attack wood, food or clothing.

But some people detest finding any insects indoors, and hygienic establishments such as hospitals have zero tolerance for them.

According to a report by the University of Kentucky, the beetle is native to Asia (e.g., China, Russia, Korea, Japan), where it dwells in trees and fields, preying on aphids and scale insects.

The first field populations in the United States were found in Louisiana in 1988.

Since then, the beetle has expanded its range to include much of the U.S. and parts of Canada.

During the 1960s to 1990s, the U.S. Department of Agriculture attempted to establish the Asian lady beetle to control agricultural pests, especially of pecans and apples.


Some scientists believe that current infestations in the U.S. originated not from these intentional releases, but from beetles accidentally transported into New Orleans on a freighter from Japan.

At present, Asian lady beetles appear to have few natural enemies. A small percentage of beetles are parasitized by tiny wasps and flies. The beetles secrete a foul smelling yellowish fluid from their leg joints when disturbed.

Some mortality occurs at sub-freezing temperatures, although survival is enhanced within buildings and other protected locations if adequate moisture or humidity is available.


Swarms of lady beetles typically fly to buildings in September though November, depending on locale and weather conditions.

Beetle flights are heaviest on sunny days following a period of cooler weather, when temperatures return to at least the mid-60s. Consequently, most flight activity occurs in the afternoon and may vary in intensity from one day to the next.

Studies have shown that Asian lady beetles are attracted to illuminated surfaces. They tend to congregate on the sunnier, southwest sides of buildings illuminated by afternoon sun.

Dwellings near woods or fields are especially prone to infestation, although those in other locations can be infested as well.

Once the beetles alight on buildings, they seek out crevices and protected places to spend the winter.

They often congregate in attics, wall cavities, and other protected locations.

Typical locations include cracks around window and door frames.

Structures in poor repair with many cracks and openings are most vulnerable to infestation.

As temperatures warm in late winter/early spring, the beetles once again become active. This usually occurs first on the sunnier, southwest side of the building. As awakening beetles attempt to escape to the outdoors, some inadvertently wander inward, emerging from behind baseboards, walls, attics, suspended ceilings, etc. Since lady beetles are attracted to light, they are often seen around windows and light fixtures.

When large numbers of beetles are flying in the fall, they often land on clothing and occasionally will bite or 'pinch' if in contact with skin.

In nature, lady beetles eat other insects and have chewing mouthparts. The bite feels like a pinprick and is seldom serious.

Once the beetles are indoors, the easiest way to remove them is with a vacuum cleaner.

If you later wish to release the beetles outdoors, place a handkerchief between the vacuum hose and the dust collection bag to act as a trap.

A broom can also be used, but is more likely to result in staining when beetles emit their yellowish defensive secretion.