Asian lady beetles are often mistaken for native ladybugs. This confusion arises from their similar appearance and widespread presence, particularly as they seek shelter indoors. Understanding the distinctions between these insects clarifies interactions with humans and the environment.
Identifying the Asian Lady Beetle
The Asian lady beetle, Harmonia axyridis, has distinct physical characteristics. While native ladybugs are typically bright red, Asian lady beetles exhibit a wider range of colors, from orange to yellow and even black. Their bodies are generally oval and slightly larger, measuring about 0.19 to 0.3 inches (5 to 8 mm) in length.
An identifying feature is the “M” or “W” shaped black marking on the white area behind their head, known as the pronotum. Its presence is a reliable indicator. The number of black spots on their wing covers, or elytra, also varies significantly; some Asian lady beetles may have up to 22 spots, while others have none at all.
Understanding Their Nips
Asian lady beetles do not “bite” like mosquitoes or ticks. Instead, they can deliver a small “nip” or pinch using their chewing mouthparts. This sensation is often described as a slight pinprick or pinch, generally harmless to humans. These nips are not venomous and do not transmit diseases.
The primary reasons for this nipping behavior include curiosity, seeking moisture, or as a defensive reaction when they land on skin and feel agitated or threatened. During dry periods, they may nip in search of moisture. While most individuals experience temporary irritation, some people may have a mild skin irritation or, in rare cases, an allergic reaction to proteins released by the beetle.
Why They Enter Homes and How to Deter Them
Asian lady beetles frequently enter homes in the late fall and winter, seeking sheltered locations for overwintering. They are attracted to warm, sunny sides of buildings. This leads to congregations on exterior walls before they find their way indoors through small cracks and openings.
Once inside, they do not reproduce, lay eggs, or feed on household materials. To deter them, seal potential entry points around the home, such as cracks around windows, doors, utility pipes, wires, and vents. Repairing damaged window screens and installing tight-fitting door sweeps also prevent their entry. For beetles already inside, a vacuum cleaner is an effective, non-toxic removal method, as crushing them can release a foul-smelling, yellow fluid that may stain surfaces.