Sunday, March 11, 2001
It's become an annual event. For the last eight years these brightly colored, black-spotted beetles have used my house as a winter refuge. And why not? It's warm, dry, and snug--a perfect place to spend the long, cold winter.
Autumn gathering: In the fall they gather on the south side of the house. They crawl under the siding, and make their way inside through cracks and crevices. On mild sunny winter days we find some on every south-facing window.
They've awakened from a kind of hibernation entomologists call diapause. Ladybird beetles are perhaps best known by the entomologically incorrect misnomer, "ladybug." These small, black-spotted, bright reddish-orange beetles are familiar to almost anyone who lives in the country or tends a garden.
They are, however, beetles so I'll refer to them as ladybird or lady beetles. "Bugs " are a completely different type of insect.
Of all the creepy crawlies that inhabit our homes and backyards, lady beetles are among the most beneficial. Both adults and larvae are predators; they eat other insects, mostly pests such as aphids, scales, and even tiny caterpillars. In fact, it is their penchant for eating pests that has resulted in this most recent population explosion.
Governmental agencies have been importing and releasing exotic species of lady beetles since the early 1960s. The first releases occurred in California, where lady beetles quickly controlled a serious pest of the citrus crop. To this day, they help insure the success of the California citrus industry.
There have been many releases throughout the eastern U.S. since the success in California, but most failed or achieved limited success in a small area. In 1991, however, a species native to eastern Asia and Japan, Harmonia axyridis, was released in Louisiana. In less than three years, it worked its way up the Mississippi and Ohio valleys and has now spread through much of the east and Midwest.
Good news: The good news is that this new species is just another predatory lady beetle that gobbles up garden pests. When warmer weather returns for good, house-bound lady beetles may have a difficult time finding their way outside, so you might want to help them along. Crack windows to allow them an easy exit. Use an index card to scrape small numbers into a jar, then release them outside on a mild day.
Or if you've got thousands of them like we do, sweep them up with a vacuum cleaner and empty the bag outdoors. They'll find their way to a rocky crevice or under a slab of bark and bide their time until it's time to procreate.
Mating time: The fall aggregations are apparently a reproductive strategy that enables the beetles to avoid having to search for each other in the spring. If huge numbers emerge simultaneously, finding a mate isn't difficult. By following an olfactory trail of pheromones in the fall, when all are well fed and healthy, they avoid energetically costly searches for mates in early spring, when food may be only sporadically available.
Entrepreneurs take advantage of this behavior by collecting these hoards of lady beetles and selling them to garden centers and catalogs. But don't waste your money. When released, hoards of lady beetles disperse quickly and may actually fly miles from the release site. Appealing thought: The notion that a $25 bag of lady beetles can keep your garden pest-free is appealing, but it just isn't so. After breeding, ladybird beetles disperse to live the life of a solitary predator. If they stayed together in huge aggregations, they'd run out of food in a matter of days.
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