Native ladybug species are essentially harmless to humans, but one specific invasive species is known to “nibble” or “pinch” people. This sensation is not a true bite, as the beetle does not inject venom or draw blood for a meal like a mosquito or spider. The minor discomfort felt is instead an exploratory action carried out by the beetle.
The Truth About Ladybug Nibbles
Ladybugs, like all beetles, possess mandibles—short, strong chewing mouthparts used for grasping and consuming prey such as aphids. When a beetle lands on skin, it may use these mandibles to lightly scrape or pinch the surface, often attempting to identify the landing site. This action results in a fleeting, minor prick or slight irritation. The momentary pinch is a simple act of investigation, contrasting sharply with the sustained, piercing action of true biting insects that feed on blood.
Identifying the Invasive Culprit
The species responsible for the majority of these incidents is the Multicolored Asian Lady Beetle, Harmonia axyridis. This invasive species was intentionally introduced to North America as a biological control agent for agricultural pests. This beetle is notably more aggressive and prone to nibbling than native species.
A key visual distinction is the presence of a distinct black marking on the white plate behind the head, known as the pronotum, which often resembles an “M” or “W” shape. The coloration is highly variable, ranging from pale yellow-orange to deep red, and they may have many spots, few spots, or none at all. Native ladybugs, in comparison, tend to be a more consistent bright red with small white spots on an otherwise black head.
Behaviorally, the invasive species clusters in large groups on the sunny sides of buildings in the fall as they search for places to overwinter. When disturbed or crushed, these beetles engage in “reflex bleeding,” releasing a foul-smelling, yellowish hemolymph from their leg joints. This hemolymph can stain surfaces and trigger minor allergic reactions in sensitive individuals.
Why Do They Nibble and What to Do Next
The primary motivation behind the exploratory nibbling is the search for moisture or salt, especially during dry periods or when they are dehydrated. The beetles may also be mistaking human skin for a potential food source, such as an aphid, or a fruit surface containing sugars. If a nibble occurs, gently brush the beetle off and wash the affected area with soap and water. This action removes any residual hemolymph, which can cause minor skin irritation or a temporary red bump.
To discourage these beetles from clustering near or inside your home, focus on sealing potential entry points before the fall.
Preventing Infestation
Seal potential entry points, such as cracks around windows, doors, and utility lines, to prevent their migration indoors.
If you find them inside, use a vacuum cleaner with a hose attachment to remove them carefully.
Avoid crushing them, as this releases the staining, malodorous defensive fluid.
Reduce bright outdoor lighting near entryways, since the beetles are attracted to warm, reflective surfaces and light sources.