If you live near us in Maryland you may have noticed a huge explosion of ladybugs in or around your home recently!
First off, keep calm, because ladybugs (also known as lady beetles) will not harm you or your home. They eat aphids, not fabric or wood. Besides that, if you scare or upset them they can quickly excrete a protective smelly yellowish fluid that can stain. We know that some folks just hate insect infestations, but...these beetles are relatively harmless!
In nature, ladybugs hibernate over the winter in masses, usually in protected places like cracks in rocks, tree trunks and other warm places - including in and around your home. When one finds a suitable spot in the fall, it produces a pheromone that attracts others, so it is common to find dozens - if not hundreds - at a time. And often a few misguided beetles get confused and come into rooms through electrical outlets and other openings in walls; our outside AC unit can attest to this!
Unfortunately, there are no really good ways to handle lady beetle infestations. Once they get in, they are nearly impossible to get rid of until spring when they naturally head back outdoors. Trying to kill those that are hibernating in wall cavities is rarely effective.
Sweep them out, being mindful of the yellow secretion they can leave on walls. If you're using a vacuum to collect many at a time, make sure to release them outdoors but putting a piece of paper towel between the vacuum hose and the collection bag as a trap.
The best approach is to prevent them from coming in next fall by sealing cracks around windows, doors and roof soffits.
And by the way, “ladybug houses" sold in garden supply catalogs usually don’t do a very good job at keeping the beetles out of your home. It might just be easier to live in relative harmony together until they are back outside in the spring - doing their aphid-eating jobs!