Why Lady Beetles and Asian Ladybugs Enter Homes in Fall

 

Both lady beetles (often called ladybugs) and Asian lady beetles move into homes during the fall because they are searching for a warm, protected place to spend the winter. Unlike honey bees or ants, these beetles cannot survive the cold outdoors, so as temperatures drop, they look for any cracks or gaps in buildings to get inside and wait out the season. This instinct is called "overwintering."

 

The Biological Drive Behind Overwintering

 

Lady beetles and Asian ladybugs are cold-blooded, which means their body temperature changes with the environment. When days become shorter and temperatures decline in late summer and autumn, their internal "clock" tells them it's time to seek shelter. In the wild, these beetles would gather under rocks, inside hollow trees, or beneath bark. As homes and other buildings have become more common, the beetles now use these manmade structures as convenient hideouts.

 

How Do They Find Their Way In?

 

During sunny fall afternoons, these beetles become especially active and are drawn to south- and west-facing walls that retain warmth from the sunlight. They look for small cracks around windows, doors, fascia boards, vents, or siding. Even tiny openings are enough—if you can see daylight through a crack, a beetle can likely fit through it.

 

Differences Between Native Lady Beetles and Asian Ladybugs

 

The Asian lady beetle (Harmonia axyridis) is an introduced species, and it is much more likely to invade homes than native ladybugs. Asian ladybugs gather by the hundreds or even thousands, while native lady beetles generally do not cluster in large groups or enter homes in significant numbers.

 

What Happens After They Get Inside?

 

Once inside, lady beetles go into a resting state called diapause, which is similar to hibernation. In diapause, their body systems slow down, and they remain relatively inactive until spring. Some beetles may accidentally find their way into living spaces and become active on warm days, often causing a nuisance but not causing damage or reproducing indoors.

 

Are They Harmful in Homes?

 

Lady beetles and Asian ladybugs are not harmful to people, pets, or property. They do not eat or reproduce indoors, chew wood, or destroy fabric. However, in large numbers, they may leave behind a yellowish fluid (called reflex bleeding) as a defense against predators, which can stain walls and fabrics and has a mild odor. Some people report mild allergic reactions if they handle the beetles.

 

How to Prevent Their Entry

 

To keep lady beetles and Asian ladybugs out:

• Seal cracks around windows, doors, siding, vents, and pipes with caulk or weather-stripping before fall temperatures drop.
• Install tight-fitting screens and repair any holes or tears in existing screens.
• Make sure attic and soffit vents are covered with fine mesh.
• Use exterior door sweeps and check garage door seals.

Reducing outdoor lighting during peak invasion periods and trimming vegetation near the house can also help deter beetles.

 

Summary

 

In summary, lady beetles and Asian ladybugs come into homes in the fall because they are looking for a warm, safe place to survive the winter. This is a natural survival behavior triggered by the seasonal change. While they do not cause significant harm, sealing up entry points before fall will keep these helpful insects outside where they belong.