The term “fake ladybugs” often refers to the invasive Multicolored Asian Lady Beetle (Harmonia axyridis), which was intentionally introduced to North America for biological pest control. While they resemble native ladybugs, their behavior is significantly different, especially their habit of invading homes in large numbers. This beetle becomes a widespread nuisance pest during cooler months when they seek shelter for overwintering. Understanding the differences between this invasive species and beneficial native ladybugs is the first step in managing their presence.
Identifying the Asian Lady Beetle
The most definitive way to identify the Asian Lady Beetle is by examining the pronotum (the area immediately behind its head). This species typically displays a distinct black marking shaped like an “M” or a “W” against a white or pale background. Native ladybugs, in contrast, usually have a black pronotum with small, white spots on the sides, often referred to as “cheeks”.
Their appearance is highly variable in color and spot count, which contributes to the confusion with native species. Asian Lady Beetles can range from a pale yellow-orange to a deep, reddish-orange, and may have anywhere from zero to 19 black spots on their wing covers. They are slightly larger than most native ladybugs, measuring about one-quarter inch in length, and have a more elongated, oval body shape.
Why They Are Considered Pests
These beetles are considered pests because of their strong tendency to aggregate in and around structures, especially as temperatures drop in the late fall. They are attracted to light-colored buildings with contrasting dark features (such as dark shutters on a light wall) and overwhelmingly prefer sun-exposed areas, like south- or west-facing walls. Upon finding a suitable overwintering site, they release a chemical pheromone that attracts hundreds or even thousands of other beetles, leading to a mass invasion.
When disturbed or crushed, the Asian Lady Beetle defends itself by “reflex bleeding,” releasing a foul-smelling, yellowish fluid from its leg joints. This oily secretion can permanently stain walls, furniture, and fabrics, and the odor can linger for a long time. Although they do not carry diseases or feed on wood or fabric, they can sometimes “bite” or pinch bare skin with their chewing mouthparts, which is usually described as a minor pinprick sensation.
Removing Indoor Infestations
Once the beetles have entered the home, physical removal is the most recommended and effective strategy, primarily to prevent staining and odors. It is important to avoid crushing or swatting the insects, as this triggers the release of the defensive, staining fluid. A conventional vacuum cleaner can be used to collect the beetles gently, which prevents the reflex bleeding and allows for easy disposal.
Disposal Methods
For those who wish to dispose of the collected beetles, a small amount of soapy water can be added to the vacuum canister or a separate container, as the detergent breaks the surface tension and quickly drowns the insects. Alternatively, a piece of nylon stocking or a handkerchief can be secured over the vacuum hose opening with a rubber band, creating a trap that allows the captured beetles to be sealed and disposed of outdoors.
Specialized Traps
Specialized indoor traps, such as insect light traps, can also be placed in dark areas like attics or basements, which capitalize on the beetle’s attraction to light.
Long-Term Exclusion Strategies
The most durable solution for managing Asian Lady Beetles is to prevent them from entering the structure in the first place, a process known as exclusion. This preventative work should be completed in late summer or early fall, before the beetles begin their search for overwintering sites. The beetles are capable of squeezing through tiny gaps, meaning all potential entry points must be sealed.
Caulking should be used to seal all cracks and openings. This includes areas around:
- Window frames and door frames.
- Utility lines and air conditioning units.
- Damaged window and door screens, which must be repaired or replaced.
- Attic or soffit vents, which should be properly screened to block access to voids.
Larger holes can be plugged with materials like cement, urethane foam, or copper mesh to stop them from entering wall voids and attics.
Chemical intervention can be used as a supplementary defense applied to the exterior of the home. Professional pest control applicators may apply residual insecticides containing pyrethrins or pyrethroids to the exterior surfaces, focusing on the sun-exposed areas where the beetles congregate. This perimeter treatment should be timed for early fall, before the beetles have moved indoors, to maximize its effectiveness in preventing their entry.