The multicolored Asian ladybird beetle is a newcomer and it’s giving other ladybirds a bad name.
Considering the good feelings that people have for the over 5,000 species of ladybugs around the world, that’s saying something. In Delaware, Massachusetts, New York and Ohio, ladybugs are the official state insect. In the past, they were so well thought of that they were used as medicine.
In the 1800s, physicians in the UK and in North America used them to treat measles. They associated their spots with the spots on their patients. They also thought that ladybugs could cure colic and that mashed ladybirds stuffed in the cavity of a tooth would control pain.
People in rural Germany think that spotting a ladybug with seven or fewer spots means a good harvest. In central Europe, they used to believe that if an unmarried woman managed to capture a ladybird and it crawled over the back of her hand, she would be married within the year.
Between 1910 and the 1970s, there were numerous planned and accidental introductions of the Asian ladybug (Harmonia axyridis) into the United States without any significant success. Then, in 1988, the beetle was discovered in Louisiana. Entomologists believe that the ladybug arrived accidentally in Baton Rouge and managed to establish itself.
By 1994, the beetle had been reported throughout the contiguous states and into Mexico and southern Canada. This, in and of itself, isn’t a problem. The problem comes from the the reasons why they’ve established. Each female Asian ladybug lays a lot more eggs than our native species (500 to 700) and there are several generations per year.
Asian ladybirds live over three years as opposed to one year for most natives. As an introduced species, they have no natural enemies here. When startled, they play dead and most vertebrate predators won’t eat a “dead” insect. They give off a rather offensive odor when alarmed that drives predators away.
They have no particular niche like many native ladybugs. They’ve been collected in trees, in crops, on beaches and in buildings just to name a few sites where they can live. They are an excellent predator of aphids, caterpillars, mites, scales, thrips and other small pests but their voracious appetite doesn’t stop with eating pests.
Asian ladybirds eat the good guys as well. As I mentioned earlier, the state of New York has a native ladybird beetle as its state insect. Since the introduction of the Asian ladybug, their state insect has disappeared.
Another drawback to the Asian ladybird beetle, and the one about which I receive the most calls this time of year, is their tendency to spend the winter, sometimes in huge numbers, in people’s houses. When the Asian ladybug finds a suitable site to hunker down and sleep through the cold months, they emit what is called an “aggregation pheromone.”
This is a chemical that calls to other Asian ladybugs saying, “This is a great place. Why don’t you come and stay here with us?” It’s not unusual for someone to contact me about finding thousands of Asian ladybirds under their siding, in their windows and doors or other cracks, crevices or other small openings.
At first, most people are amused or curious about their visitor. But, like some in-laws, their entertainment value rapidly decreases as their numbers increase. Asian ladybugs are large enough (6 mm) to bite.
When disturbed, they give off a foul odor and, if crushed, will leave a stain on drapes, carpeting and furniture that is almost impossible to remove. If you try to paint over it, the stain will just seep through the new coating.
To prevent them from invading your house, your home should be tightly sealed; not only from the cold winds of Old Man Winter, but from these pests as well. Doors, windows and attic vents all should be inspected in the early fall for small openings. Once you’ve spotted the gaps, you should fix them as soon as possible.
If you find the ladybugs outside aggregating on the side of your house, spray them with a garden hose to discourage them. If you find these Halloween-colored invaders in your house, a vacuum works well to suck them up en masse. After vacuuming them up, remove the bag and take the beetles outside to a sheltered location.
Remember, inside they’re not good. Outside, when they wake up next spring, they’re a cost-free benefit for your garden.
Tim Lockley, a specialist in entomology, is retired from a 30-year career as a research scientist for the U.S. Department of Agriculture. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.