Hordes of Ladybugs

Are you besieged by ladybugs? This time of year, as summer’s warmth ebbs away, they assemble in warm places to bivouac for winter. They are especially interested in locations that are exposed to the winter's sun, so that they are warmed on sunny days. In nature, they look for crevices in the bark of trees, but they are perfectly happy if they find a narrow channel around a window that leads into a house, especially if the opening is on the sunny southern exposure. If one finds a good place to take refuge, it sends out the call and hundreds follow. They use pheromones, chemicals to which they are extremely sensitive, to locate each other.

So if they've found a way into your house, they'll be with you until spring, and if they plagued you last year, they’ll be back! If their tactics overwhelm you and a rampant horde invades, try vacuuming them up and releasing them outside (next to someone else's house). You can even take off the vacuum bag and leave that outside--the beetles will emerge from it in the spring. If you pick them up or sweep them, you'll notice that they bleed as a defensive mechanism. Be warned that the blood smells (and tastes!) unpleasant and will stain fabric. In addition, they also bite, but not very strongly.

If the ladybugs have occupied your house, they are entering through cracks, often around windows and doors. The only way to prevent them from overrunning your house is to caulk any cracks. Caulking will decrease your energy bills and is one way you can contribute to energy efficiency--a big plus for the environment. So the ladybugs are really just pointing out something you need to address anyway. Thank them while you vacuum them up and return them to the outdoors!

Most of the ladybugs that enter houses are the Multicolored Asian Ladybug. We have several native species of ladybugs in this area, but they rarely congregate inside houses, bleed, or bite. The Asian ladybugs are easiest to identify by carefully observing their white “neck,” called the pronotum, which is just behind the tiny black head and in front of the orange wing covers. On the Asian species, the white pronotum has a black letter “M.” Our native species of ladybug also have black and white pronota, but none has the distinctive M. The background color of the Asian ladybugs’ wing covers ranges from orange to pale yellow, and they may have many, few, or no black spots.

They are called Asian ladybugs because they are an exotic species, introduced here from Asia. Like many other exotics, they have rapidly multiplied because our environment is similar to their native Asian environment, with the exception that here they have no natural enemies.

Ironically enough, these beetles were imported for use in organic gardening. Their larvae, especially, are effective predators of aphids and other soft-bodied insects. A legion of ladybug larvae will rapidly overwhelm garden pests, and many garden catalogs sell throngs of ladybugs as biological controls. So far as I’m aware, they are not causing any harmful environmental effects, but they’ve only been here about 10 years (1988 was the first documented specimen collection). Most folks with hordes of ladybugs inside their homes would already argue that they are pests. I don't know how long it took before kudzu, another Asian exotic species that was purposefully introduced, was viewed as a pest instead of a benefit!

PHOTO CAPTION: The exotic Multicolored Asian Ladybug. It has a black “M” on its otherwise white “neck.”

Text and photos may not be used without the author's permission