Like the larvae, adult lady beetles are voracious predators, consuming scores of aphids a day. Aphids are daunting garden enemies, which makes lady beetles a gardener’s best friend.
Nevertheless, when these insects converge on our homes en masse in late August or September (depending on the region), they can become a real nuisance. Most often, it is the multicolored Asian lady beetle (I]Harmonia axyridis) that infiltrates buildings in the fall. They can be seen swarming on the exterior siding. When disturbed, their natural defense is to secrete a brownish substance, so they may leave behind marks on the siding. And they sometimes even bite—not hard enough to break the skin, but enough to startle you.
Asian lady beetles look for structural openings where they can huddle into groups and hibernate. When the temperature warms up, they gather at windows, attracted by the light. Inevitably, some of the hibernating insects can’t find their way back outside come spring. Their carcasses accumulate and attract larder beetles, which take up residence in the walls and eventually find their way into the rooms of your home.