Asian lady beetles are a common sight, especially as cooler weather approaches. Often mistaken for native ladybugs, these insects frequently congregate around homes and other structures. Their presence often leads to questions about their behavior and potential contact with humans.
The Truth About Their Bites
Asian lady beetles can “bite” humans, though this action is more accurately a nip or pinch. Unlike mosquitoes, they lack true biting mouthparts designed to pierce skin for blood. Instead, their mandibles are primarily used for chewing insect prey like aphids. When they contact human skin, they may use these mouthparts, causing a sensation similar to a pinprick. This contact is not intended to feed on humans and typically does not break the skin.
Why They Bite
Asian lady beetles typically nip humans out of defense or in search of moisture. They are not aggressive but may react if threatened, handled, or seeking moisture on dry skin. During fall, as they seek sheltered locations to overwinter, they often congregate in large numbers on buildings and sometimes enter homes. This increased human interaction can elevate the likelihood of defensive nips.
What a Bite Feels Like
A nip from an Asian lady beetle usually feels like a mild, fleeting pinch or pinprick. The sensation is momentary and rarely causes more than minor irritation. These nips are harmless and do not transmit diseases to humans. While most experience no lasting effects, some might have a mild allergic reaction, manifesting as a small, raised red bump or slight swelling.
Identifying Asian Lady Beetles
Distinguishing Asian lady beetles from native ladybugs is important due to behavioral differences, especially regarding indoor presence. Asian lady beetles are typically oval-shaped and slightly larger than native ladybugs, measuring about 0.2 to 0.3 inches long. Their coloration varies widely, ranging from yellow, orange, to red; some forms can even be black with red markings. They can have anywhere from zero to 20 black spots of variable size on their wing covers, which may fade with age.
A key identifying feature is a distinct black “M” or “W” shaped marking on the white area behind their head, known as the pronotum. Native ladybugs typically lack this specific marking, often having a black head and thorax with small white spots on the sides instead. Asian lady beetles are also known for their tendency to gather in large numbers on the sunny sides of buildings, seeking entry points to overwinter indoors.
Managing Their Presence
Preventing Asian lady beetles from entering homes is the most effective management strategy. Sealing cracks and openings around windows, doors, pipes, and utility wires with caulk or other sealants can block their entry. Repairing damaged window and door screens also helps deter them.
If beetles are already inside, remove them gently without crushing them. Vacuuming them up is an effective method; use a shop vac or place a nylon stocking inside the regular vacuum hose to collect them. Crushing them releases a foul-smelling, yellowish fluid called hemolymph, their defensive mechanism, which can stain surfaces like walls, carpets, and furniture. After vacuuming, release the collected beetles outdoors far from the home.