Ladybugs are beneficial insects, valued for natural pest control. While typically viewed as harmless, some types can cause concern, leading to questions about their defensive properties or if they are “poisonous.”
Understanding Ladybug Defenses
Ladybugs are not typically “poisonous” to humans, but they do employ effective defensive mechanisms. When threatened, many species engage in reflex bleeding (autohaemorrhaging), releasing a yellowish, foul-smelling, and bitter fluid called hemolymph from their leg joints. This hemolymph contains alkaloids that deter predators. The unpleasant taste and odor of this fluid signal to potential attackers that the ladybug is unpalatable. While this fluid can cause mild irritation or staining on surfaces, its primary purpose is to discourage predators.
Identifying the Asian Lady Beetle
The Asian Lady Beetle (Harmonia axyridis) is frequently confused with native ladybugs and is often responsible for more noticeable defensive behaviors. Distinguishing this beetle involves several key characteristics. One prominent identifier is a distinct “M” or “W” shaped black marking on the white area behind its head, known as the pronotum.
Asian Lady Beetles exhibit a wide range of colors, from orange to dull red, and can even be yellow or, rarely, black. Their spots are also highly variable; they may have many spots, a few, or even no spots at all. These beetles are typically slightly larger and more oval in shape compared to many native ladybug species, which tend to be rounder. A significant behavioral clue is their tendency to aggregate in large numbers indoors during the colder months.
Effects on Humans and Animals
Encounters with Asian Lady Beetles can result in common, mild effects. For humans, contact with their hemolymph can lead to skin irritation, such as mild allergic reactions or itchy bumps. The fluid can also stain light-colored surfaces and produce an unpleasant odor. While they can pinch, especially when disturbed, severe reactions or serious bites are rare, and they do not carry diseases.
For pets, particularly dogs, ingesting a large number of Asian Lady Beetles can cause gastrointestinal upset, leading to symptoms like vomiting, lethargy, or a reduced appetite. The bitter chemicals in their hemolymph can be corrosive and cause chemical burns or irritation in the mouth and digestive tract. In unusual cases, beetles may attach to the roof of a pet’s mouth, requiring veterinary attention for removal. Ladybugs, including the Asian Lady Beetle, are generally not a serious health threat to humans or animals.