Ladybugs are generally seen as harmless, beneficial insects. However, certain species, particularly the Asian Lady Beetle, can become a nuisance. This article clarifies what makes some ladybugs problematic and how to manage encounters with them.
Defining “Poisonous” in Ladybugs
Ladybugs are not truly poisonous to humans; ingesting them does not typically cause severe internal poisoning. The concern with certain species, such as the multicolored Asian Lady Beetle (Harmonia axyridis), stems from their defensive mechanisms and behavior. These beetles are considered “problematic” due to the substances they release when disturbed or their tendency to infest homes. Their impact comes from these secretions, potential minor bites, or large indoor gatherings, rather than from being toxic if merely touched.
Identifying Problematic vs. Beneficial Ladybugs
Distinguishing between beneficial native ladybugs and the Asian Lady Beetle involves observing physical characteristics. Asian Lady Beetles (Harmonia axyridis) exhibit a wide range of colors, from pale yellow to bright red, and can have varying numbers of black spots. A key identifying feature is the distinct “M” or “W” shaped black marking on the white area behind their head (pronotum). Native ladybugs are typically bright red with distinct black spots and usually lack this specific head marking. Asian Lady Beetles also tend to be slightly larger and more oval-shaped than native species, which are generally rounder. Behaviorally, Asian Lady Beetles often swarm and invade homes in large numbers in the fall, a behavior less common for native species.
Risks Associated with Problematic Ladybugs
The Asian Lady Beetle’s defensive behaviors can cause minor issues for humans and pets. When disturbed, they engage in “reflex bleeding,” releasing a foul-smelling, yellowish fluid (hemolymph) from their leg joints that can stain surfaces like furniture, walls, and fabrics. While uncommon, Asian Lady Beetles can deliver a small bite that feels like a pinch or pinprick, though it is not serious and does not transmit diseases. In sensitive individuals, prolonged exposure to large infestations or their secretions can trigger allergic reactions, including skin irritation, runny nose, sneezing, itchy eyes, coughing, and asthma. For pets, ingesting many beetles can lead to gastrointestinal upset, such as drooling, vomiting, or diarrhea, and in rare cases, their hard exoskeletons might cause minor mouth irritation.
Managing Encounters with Ladybugs
Managing ladybug encounters, especially with indoor Asian Lady Beetle infestations, typically involves non-toxic methods. Preventing entry is the most effective approach; seal cracks around windows, doors, and utility entry points. For existing indoor populations, gentle removal avoids triggering defensive secretions. Sweeping them into a dustpan or using a vacuum cleaner with a hose attachment are effective collection methods.
If vacuuming, use a shop vac or secure a nylon stocking inside the hose to collect beetles without staining your main vacuum. Once collected, they can be released outdoors away from the house or disposed of. Avoid crushing them, as this releases staining hemolymph and an unpleasant odor. Outdoor management generally involves allowing them to prey on garden pests, as they are beneficial. For severe indoor infestations, consider contacting a pest control professional.