The Multicolored Asian Lady Beetle (Harmonia axyridis), often referred to as the “Japanese ladybug,” was intentionally introduced from East Asia to manage agricultural pests like aphids. The direct answer is yes, this species can nip or bite humans, a behavior uncommon among most native ladybug species. The Asian Lady Beetle is now widely recognized as an invasive species, competing with native ladybugs and becoming a significant household nuisance, especially when it seeks to overwinter indoors.
Identifying the Asian Lady Beetle
Identifying Harmonia axyridis is key, as it looks similar to beneficial native ladybugs but behaves differently. The physical appearance of the Asian Lady Beetle is highly variable, leading to its common name. While native ladybugs are often a consistent red, this species ranges in color from pale orange and yellow to deep red or black. The number of black spots on its wing covers is inconsistent, varying from none to nineteen or more. The most reliable distinguishing feature is a prominent black marking on the white or pale section behind the head, called the pronotum, which often forms a distinct “M” or sometimes a “W” shape.
Understanding the Nipping Behavior
The physical interaction with humans is technically a nip or a pinch using its chewing mouthparts, rather than a bite meant for feeding or injecting venom. This action is generally described as a slight prick or irritation and does not typically break the skin or draw blood. The Asian Lady Beetle is not venomous and does not transmit diseases to humans. The motivation behind the nipping is not aggression but a response to environmental pressures. Beetles may be searching for moisture or salt, especially when they aggregate indoors during cooler months when resources are scarce. In rare instances, contact with the beetles or their secretions may cause minor allergic reactions in sensitive individuals, such as itching, redness, or sinus irritation.
Dealing with Nuisance and Prevention
Beyond the mild nipping, the Asian Lady Beetle creates a nuisance primarily through its autumn and winter behavior. As temperatures drop, these beetles swarm and congregate on the sunny walls of homes, seeking warm voids for overwintering. They often enter structures through small cracks, vents, or gaps around windows and doors, sometimes in massive numbers. When disturbed or crushed, the beetles exhibit a defensive reaction known as “reflex bleeding,” releasing a foul-smelling, yellowish fluid from their leg joints. This fluid can permanently stain walls, fabrics, and furniture. The most effective prevention method is to seal all exterior cracks and crevices before the fall, focusing on areas where pipes, wires, and utility lines enter the home. If beetles are already indoors, remove them without crushing them, typically by vacuuming them up and then sealing and discarding the vacuum bag.