Why Ladybugs Swarm on Your House
All of a sudden, on a warm, sunny day, swarms of ladybugs converge on the sunny exterior of your house, garage or shed. Don't you hate it when that happens?
Why They Do It
Ladybugs swarm because they're looking for a warm place to hibernate for winter.
They hibernate in clusters. When one of them finds a suitable place, it releases a pheromone that attracts a couple gazillion more of them. In fact, the pheromone can keep the ladybugs coming back year after year.
Not content to just sit there soakin' up the rays and workin' on their tans, they enter the house in droves. The kids don't have to stand there holding the door open, either.
Ladybugs simply find loose-fitting screens, cracks, and vents, and soon enough, they're house guests. It’s a phenomenon that causes a great deal of exasperation. And they don't even have a name for it!
When and Where It Happens
This phenomenon happens every fall in the eastern U.S. and Canada. In southern New England where I’m from, it occurs on warm, sunny days in October and even into early November.
Ladybugs appear to be most attracted to houses with natural wood siding, houses in wooded areas, light-colored houses warmed in sunlight, and older houses with lots of crevices.
While they are pests, they're not harmful to humans or pets, and they don't reproduce during hibernation or damage structures.
Prevention Is the Best Solution
- To keep the bugs from getting in, repair loose-fitting windows and doors, seal cracks, and secure vents.
- If they get in, suck them up with a vacuum cleaner and release them outside, otherwise the survivors can crawl out of the bag and re-infest your house.
- Their bodily fluids are smelly and can stain, so avoid squishing or sweeping them.
- If you want to use an insecticide on them, select one that has pyrethrin as the active ingredient. Pyrethrin is a derivative of the chrysanthemum plant and is safer than permethrin, which is highly toxic to cats.
Interesting Facts About Ladybugs
- Ladybugs are a kind of beetle.
- Superstition has long held that they are a symbol of good luck and that killing one is bad luck. My hunch is that this superstition has resulted in far more ladybug lives being saved than episodes of good fortune.
- There are some 400 species of ladybugs in the U.S., and most of them are beneficial.
- Worldwide, there are over 40,000 different species of beetles.
- Ladybugs are voracious predators, consuming aphids and other insects that are harmful to plants. That's the silver lining in this cloud of ladybugs. If you have houseplants, it may behoove you to become a ladybug rancher.