Invasion of the Ladybugs

Ladybug on the windowsill.

Every new year – sometimes in January, sometimes not till March, my house is invaded by ladybugs. At first they congregate on the sunny upstairs windows. Before long they are downstairs too. Within a week or two, they seem to be everywhere – scooting across the kitchen counter, flitting around the light fixtures, crunching underfoot in the dust on the stairs.

I can’t say that I mind. If our house had to be infested with some sort of insect, I’d happily choose ladybugs any day. After all they’re the official state insects of both Massachusetts and New Hampshire -- and they don’t bite, or eat wood, plants or paper. With their small, dome-like, red or orange bodies accented with black dots, I find them rather cute.

According to a Cornell University web page, ladybugs (Coleoptera: Coccinellidae) are “among the most visible and best known beneficial predatory insects.” Also known as lady beetles or ladybird beetles, there are over 450 different species in North America alone – some native, others originating abroad.

Ladybugs are considered beneficial because they feed primarily on aphids, mites, and other insects that you don’t want in your home or garden because of what they eat or the diseases they carry. Farmers often import ladybugs to help chase away aphids or other pests. In particular, vegetables, grains, strawberries, legumes and tree crops all benefit from their presence. Certain species of ladybug can eat as many as 300 aphids per day!

But why do they show up in my house each winter? Adult ladybugs essentially hibernate through the cold months, getting cozy under leaf litter, rocks or bark, or in protected areas such as buildings. They need cool, dry places to conceal themselves from their predators, and will just as often choose to snuggle in under the shingles or siding of a building rather than come inside.

Ladybugs probably move into (or onto) the house in the late fall, but don’t reveal themselves until later in the season when they are lured out of hibernation by the warmth of the sun. On a sunny day, a ladybug will be attracted to the radiant heat of a window with a southern exposure. Once awakened, it will start crawling – and flying -- around.

In the spring, the ladybugs emerge from their winter hiding places, and depart to find better sources of food and places to lay their eggs. By early summer, a female ladybug may lay between twenty and 1,000 eggs. Once hatched, the adults will live from a few months to over a year. Ladybug life consists of mating, searching for food, and preparing for hibernation.

At my house, I find the ladybugs’ presence reassuring. They are usually relatively few in number, and I know that they’re snacking on critters that I never wanted at home in the first place. But if your house is visited by great swarms of ladybugs, or if you just have an aversion to bugs, however cute, these little ladies might start to get on your nerves. Once they’re in, there’s not much you can do about them. But take heart – they will be going away any day now.

Sources: www.nysaes.cornell.edu/ent/biocontrol/predators/ladybintro.html, and www.ipm.msu.edu/asianladybeetle.htm

By Kezia Bacon-Bernstein, Correspondent
March 2005

Kezia Bacon-Bernstein's articles appear courtesy of the North and South Rivers Watershed Association, a local non-profit organization devoted to the preservation, restoration, maintenance and conservation of the North and South Rivers and their watershed. For membership information and a copy of their latest newsletter, contact NSRWA at (781) 659-8168.