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MADISON, Wis. (CIVIC MEDIA) – Suddenly, Fall arrives and windows, walls, and surfaces are covered in these orange-spotted invasive beetles.
Sometimes called “Halloween beetles” what you’re seeing is the Asian lady beetle, busy with their annual invasion of homes in October.
Belonging to the Coccinellidae family, which encompasses various small beetles often referred to as ladybugs, lady beetles, or ladybird beetles, the Asian lady beetle (Harmonia axyridis) has turned up in Canadian and U. S. homes in recent years. This year seems to be a bit worse.
They were introduced to North America in the 1970s along with other aphids and other crop-eating insects. They spend the summer dining on hundreds of soft insects, or in corn and soybean crops until the harvest.
When temperatures start to drop, and the fields have been harvested, they leave in search of warmer temperatures. This is why you’re most likely to find them gathered in large clusters clinging to brick, pavement, or windows, trying to absorb the heat.
While they are mostly harmless, Asian lady beetles that enter your home for the winter won’t do damage, spread disease or reproduce inside. They do, however, have an unsettling defense mechanism.
It’s called “reflex bleeding,” and if threatened, they’ll bleed from their joints, releasing a smelly substance that can leave a stain.
You’ve probably been calling them “ladybugs” your entire life, but technically, that isn’t correct. That’s because they aren’t bugs; they’re beetles. Native lady beetles are red with black spots. The multicolored Asian lady beetle can range in color from tan to yellow to orange to red.
Another way to tell them apart is by looking at the back of the head, the thorax, which has a black ‘M’ shape. Their bodies are also slightly longer and more oval, whereas native lady bugs are rounder.
Unlike other insects, which only live for a few weeks, this species can live up to three years. When it finds a spot it likes, it will lay down a pheromone so it can return the following year.
Asian lady beetles are aggressive, and they tend to take over habitats, displacing native species. They also bite, unlike native species. Bites feel like a pinch, but they can break the skin.
If you want to prevent them from getting inside, install screens, caulking, and weather stripping. Focus on the sunny, southwest sides of your home because these areas tend to be more infested with them.
North America is home to hundreds of lady beetle species that survive winter by riding out the cold weather indoors.
