Quick facts
- Size
- About 1/4 to 3/8 inch
- Looks like
- Orange to red, variable spots, M or W mark behind head
- Peak season
- October, especially warm days after a cold snap
- Where in Michigan
- Statewide, worst near woods, orchards and farm fields
- Main risk
- Nuisance, minor bites, staining, odor
- Risk level
- Low
Signs you have asian lady beetles
- Hundreds of beetles on sunny south or west walls on warm fall afternoons
- Beetles crawling around windows and ceiling lights on warm winter days
- Yellow-orange stains on walls, curtains or window sills
- A sharp, musty smell when beetles are disturbed
- Dead beetles piling up in light fixtures and window tracks
Why Asian lady beetles swarm Michigan homes in October
Multicolored Asian lady beetles were brought to North America to help control aphids on crops and trees. They do that job well all summer in Michigan orchards, soybean fields and woodlots. In fall, they look for protected places to spend the winter. In their native range they gather on sunny cliffs. Here, the closest thing is the warm south or west wall of your house.
The swarms usually happen on the first warm, sunny afternoons after a cold snap in late September or October. Homes near woodlots, orchards and soybean fields see the heaviest numbers, and houses that stand out on a hill or at the edge of a field seem to attract more. Light-colored siding that reflects sun can draw them too.
From the wall, they crawl into gaps around windows, siding, soffits and roof vents. Most spend winter in wall voids and attics. On warm winter days and in early spring, some lose their way and end up in living space, often on upstairs windows and around ceiling light fixtures, sometimes in large numbers.
How to tell them from native ladybugs
Asian lady beetles vary from pale yellow-orange to deep red, with anywhere from no spots to many. The easiest clue is a black M or W shaped mark on the white area just behind the head. Native lady beetles are usually smaller or more uniform in color and do not gather on houses in large numbers in fall.
They can give a small pinch when they land on skin, which surprises people. When disturbed, they release a yellowish fluid from their leg joints that smells bad and can stain light fabrics, curtains and walls. Some people report allergy symptoms in homes with heavy numbers, so cleanup matters more than it might seem.
Keeping lady beetles out of your house
Sealing works better than anything else. In September, before swarms start, caulk gaps around window and door trim, siding corners, fascia boards and utility lines. Screen roof, soffit and gable vents with fine mesh. The same work keeps out stink bugs and cluster flies, so one round of sealing pays off three ways.
An exterior treatment applied by a licensed applicator in late September, following the label, can reduce the number that get in. Inside, use a vacuum instead of a broom. A knee-high nylon stocking pushed into the hose and held with a rubber band lets you catch them without crushing, then release them outdoors or dispose of them.
What you can do yourself
- 1Caulk and seal exterior gaps in early to mid-September.
- 2Repair window screens and screen attic and soffit vents.
- 3Vacuum beetles indoors rather than sweeping or crushing them.
- 4Put a stocking inside the vacuum hose to catch beetles and avoid stains.
- 5Use a light trap in the attic if many are getting in there.
When to call a licensed pro
- You get large swarms every October despite sealing.
- Beetles keep coming into living spaces through winter.
- Gaps are high on the house and need ladder work.
What asian lady beetles treatment costs in Michigan
$150 to $400per treatment
Typical Michigan ranges, not quotes. Price depends on home size, height and whether exclusion work is included with the exterior treatment.
Typical ranges, not quotes. See the full Michigan pest control cost guide.
Asian lady beetles: common questions
Do Asian lady beetles bite?
They can pinch, especially when they are hungry or warm in fall. The bite feels like a small prick, may leave a tiny red mark, and does not spread disease. Brushing them off gently instead of swatting avoids stains.
Will Asian lady beetles reproduce in my house?
No. They overwinter in walls and attics but do not feed or lay eggs indoors. They mate and lay eggs outside in spring, so numbers inside do not grow during the winter.
When do Asian lady beetles leave in spring?
Most leave on warm days in March and April as they try to get back outdoors. Some head toward light inside instead, which is why you see them on windows and lamps. Vacuum those and seal the gaps before next fall.
Is it the same bug as the ladybug in my garden?
It is a type of lady beetle and it eats aphids like native species do, but it is not native to Michigan. The tell is the M or W mark behind the head and the habit of swarming houses in fall.