Ladybug Invasions Normal, says Expert

Ladybug Invasions Normal, says Expert

By Barbara Pitoniak

Have you noticed many more ladybugs in and around your home or workplace these days?

Your observations are accurate, says a UMass Extension specialist who reports that swarms of hundreds, and in some places, even thousands, of the tiny critters have lately been observed.

Craig Hollingsworth, entomologist and Integrated Pest Management specialist, uses a bit of entomological history to explain the large number of ladybugs.

According to Hollingsworth, a number of times between 1978 to 1981, the U.S. Department of Agriculture attempted to introduce the multicolored Asian lady beetle Harmonia axyridis (H.a.) to the eastern United States. It was hoped the beetles would help to control aphids and scales, including the Hemlock Woolly Adelgid, a pest currently plaguing the Northeast. Harmonia axyridis was not observed again, however, until 1988, in Louisiana. The 10-year lag, says Hollingsworth, between release and recovery indicates that perhaps USDA's efforts did not succeed and that the introduction of the beetles to Louisiana was an "accidental" one, possibly from an Asian ship.

Hollingsworth says that last year, sitings of H.a. were made all along the Atlantic coast, up into Maine and Canada. The beetles were also found in the Pacific Northwest, especially in Oregon, and they were also detected on a planeload of Christmas trees bound for Hawaii.

"Last year, the West Virginia Department of Agriculture received 100 calls in one day about swarms of lady beetles," says Hollingsworth. "In Massachusetts, we also recorded sitings from the Berkshires to the Cape."

The beetles, which have no native natural enemies, have increased their numbers during the summer months. Now that the days are becoming shorter, and the weather cooler, Hollingsworth explains, they are seeking sheltered sites for overwintering. As one beetle finds an appropriate site, it will emit what's called an "aggregating pheromone," or a chemical which attracts other beetles.

"I've observed most of them on sunny days in southern exposures," says Hollingsworth. "If the ladybugs find entry to a house, they're likely to exploit it, gathering a mass of dozens to thousands of beetles. They'll stay through the winter, without feeding, and when the weather warms, they'll disperse."

What to do about the tiny beetles? Hollingsworth advises that homeowners start by sealing up all the cracks in their home's foundation or siding. He doesn't recommend sweeping the ladybugs. "They're 'reflex bleeders' -- when disturbed, they bleed from their joints -- and their blood smells bad," he says. "Vacuum them up instead. If you use a clean vacuum bag, you can store them in a cool spot like an unheated shed or garage, and let them go in the spring. They'll help control aphids and scale in trees."

"A neat thing about these beetles," says Hollingsworth, "is that they're multicolored. Usually, you can identify a ladybug to species by its color and spot pattern. But not these. You find yellow and orange beetles, without spots, or with up to as many as 19 spots."


Click here to return to the main ladybird beetle homepage.