Ladybugs swarming in the house: 5 cheap ways to deal with lady beetles

If your house turns into a beetle magnet on the first warm afternoon in October, you are not imagining it. Across much of the US, lady beetles gather on sunny walls by the hundreds or thousands every fall, then spend the next few weeks finding every gap in your window trim. The good news: they do not damage wood, eat food or breed indoors, and you can deal with most of them for the price of a tube of caulk and an old stocking.

First, it probably is not a “real” ladybug

The swarmers are almost always multicolored Asian lady beetles. They were brought to the US on purpose as a biological control for aphids on crops and trees, and they are very good at that job. They are also very good at finding their way indoors, which native ladybugs rarely do.

How to tell them apart:

• Color: Asian lady beetles range from pale yellow-orange to deep red, with anywhere from no spots to many. Native species tend to be more uniformly red.
• The M mark: look at the white area just behind the head. Asian lady beetles usually have a black marking there shaped like an M or a W, depending on which way you look.
• Behavior: only the Asian species tends to gather on houses in large numbers in the fall.

When they are disturbed, they release a yellowish fluid from their leg joints. It smells unpleasant and can stain light walls, curtains and fabric, which is the main reason not to crush or swat them.

Why your house, why now

Once the first cold nights arrive, the beetles look for a protected place to spend the winter. In the wild, that is a rock face or a cliff. On a street, it is a house, especially one that is light-colored, sunlit on the south or west side, and near fields or woods. They gather in the afternoon sun, crawl behind siding and into wall voids, and settle in. On warm days all winter and into spring, some wander toward the heat and light inside your rooms. That is why you find them on windowsills in February even though you have not seen one outside in months.

5 ways to deal with a lady beetle swarm

1. Vacuum them up, stocking first

This is the gentlest, cheapest and most effective indoor method. Push a knee-high nylon stocking or the foot of an old pair of pantyhose a few inches into the vacuum hose or wand, fold the open end back over the outside of the hose, and hold it with a rubber band. When you vacuum, the beetles collect in the stocking and never reach the bag or canister, so your vacuum does not end up smelling of them.

When you are done, pull the stocking off carefully, tie it closed, and either release the beetles outside, well away from the house, or put the tied stocking in the freezer overnight and then throw it away. Do not leave beetles loose in a bagless canister; they will crawl back out.

2. Seal the gaps they use

Keeping them out is the long-term fix, and it saves on heating bills at the same time. Do this in late summer or early fall, before the swarms start.

1. Walk around the outside of the house on a sunny fall afternoon and watch where the beetles gather. That tells you which walls matter most.
2. Caulk gaps around window frames, door frames, and where pipes, cables and dryer vents enter the house. A tube of exterior caulk usually costs a few dollars.
3. Add or replace door sweeps and weatherstripping on exterior doors.
4. Repair torn window screens and make sure screens fit tightly.
5. Cover attic, soffit and crawl space vents with fine screen if they are open, leaving them vented.

Check with your local cooperative extension office if you are unsure what to seal on an older home; many publish free guides for your region, such as University of Minnesota Extension.

3. Knock them off outside

A strong spray from the garden hose knocks clustered beetles off siding and window frames before they find their way in. It has to be repeated on active afternoons, but it costs nothing. Some people add a little dish soap to a hose-end sprayer; it cleans the siding at the same time, but plain water does most of the work.

4. Try a light trap for the stragglers

Beetles that emerge indoors in winter are drawn to light. A simple homemade trap works: set a small lamp or night-light near a shallow pan of soapy water in a dark room, or aim a flashlight into a jar at night. Commercial lady beetle light traps also exist, but a vacuum and stocking handle most homes without buying anything.

5. Use pesticide only outdoors, and only per the label

If a heavy infestation returns every year, an outdoor barrier treatment around windows, eaves and siding in early fall can reduce how many beetles get in. Use only products labeled for this use, follow the label directions exactly, and keep kids and pets away from treated areas until the label says it is safe. Many families find it worth hiring a licensed pest control company for this one job rather than buying ladders and chemicals.

Avoid spraying inside the house. Beetles killed inside walls cannot be vacuumed out, and the dead insects can attract other pests like carpet beetles.

When the smell or stains are already there

If beetles were crushed on a wall or curtain, blot the spot with a damp cloth and a little dish soap as soon as you can; the yellow fluid is easier to lift fresh. Test any cleaner on a hidden patch of fabric first. For lingering odor in a window well or sill, vacuum every beetle out, wipe the area with warm soapy water and leave the window open for a while on a mild day.

What not to do

• Do not crush or sweep them. That triggers the smelly, staining fluid.
• Do not use bug bombs. Foggers do not reach the wall voids where beetles hide, and they coat your whole room in pesticide.
• Do not seal vents shut. Furnace, dryer and attic vents need airflow. Screen them instead.

Living with the stragglers

Even a well-sealed house will see a few beetles. Keep the stocking-lined vacuum ready near a sunny window during October and again in early spring, and think of it as a five-minute chore on warm afternoons. The same weather sealing that stops the beetles also cuts drafts, which is one of the cheapest energy fixes on the family and home tips list.

For other small household annoyances solved on a budget, see the guides to homemade laundry detergent and whether dryer balls work. And if the kids are curious about the beetles, a jar, a magnifying glass and a field guide from the library turn a pest into a free science afternoon, one of the easy TV-free activities for a rainy fall day.