Autumn Ladybug Invasions

Article: Autumn Ladybug Invasions

Ladybug beetles, also known as Asian Lady Beetles or Ladybird beetles, are a gardener's best friend in the spring and summer months. In the world of beneficial garden insects, you won't find a better predator when it comes to controlling soft-bodied pest like aphids and scale. By the time fall rolls around, however, these insect friends start wearing out their welcome when they begin to congregate on the sides of buildings and invading our indoor environments.

Asian vs. Native Species

The ladybugs accumulating on your walls and windows are most often the Asian Lady Beetle variety, although some native species will follow suit if conditions warrant. These beetles were first imported from Asia into the United States in 1916 and released as a biological control for certain species of insects. For a long time it was assumed that they failed to establish themselves, until they turned up in 1988 in New Orleans. They are currently found in every part of the United States. Asian Lady Beetles are about 1/3 of an inch long. Compared to other lady beetle species, Asian Lady Beetles come in a wider range of colors and spot numbers. Wings range from black to mustard; spots number zero to more than a dozen. The most common U.S. form is mustard to red with 16 or more black spots. The Asian Lady Beetle can also often be identified by a black mark resembling the letter "M" (or "W") located between its head and abdomen.

Ladybeetle Behavior

As part of the Asian Lady Beetle life cycle, as soon as a hard frost occurs in the fall, adult beetles look for a cool, dry place to spend the winter. Throughout their native range in Asia, a winter shelter usually consists of cavities or caves in south-facing cliffs where the temperature is cool and the air is dry. This explains why they tend to congregate on the exterior walls of south-facing buildings before sometimes making their way inside through tiny cracks and holes in your siding and insulation. They will not attack wood, fabric or people, they just want to hibernate. When the weather warms up in the spring, the ladybeetles will make a hasty retreat back outdoors.

So why do piles of dead ladybugs collect in your window sill over winter?Once inside your home, ladybugs will naturally gravitate towards the light-usually making their way to your windows. Because the temperature indoors is warmer and dryer than the temperature outdoors, the ladybeetles' metabolism gears up for summer again. A high metabolism coupled with no source of food causes them to quickly use up their winter reserves and die. This is why it's best to capture ladybeetles and return them to the outdoors where cooler temperatures will slow down their metabolism until spring.

Waking Up To The Light

For ladybeetles that hibernate inside the cracks and crevices of exterior walls, an occasional calm, sunny winter day, combined with a steady increase in daylight and a southern exposure, is often enough to generate sufficient amounts of radiant energy (temps may reach near 50º F) to wake the beetles up from their winter naps. Once they wake up they begin crawling around and sometimes make their way inside you home. This is why even though it may only be 25º F degrees outside, ladybugs can mysteriously appear in your living room in the middle of winter.

Controlling Indoor Invasions

The best way to control Lady Beetle invasions is to seal up and repair any cracks and crevices around windows, eaves, doors, insulation and siding. Pay close attention to places where pipes, conduits and wires enter your home. Planting trees near south-facing exterior walls may also offer long term control by providing the beetles shelter for the winter.

Ladybugs are tough little bugs. The best way to remove them is to use a broom, wash rag or a vacuum cleaner with a dirt trap that can be emptied (e.g. Dust Buster). If you can, return the bugs to the outdoors so they'll be around to feed on your garden pests next season. You can also release them onto your indoor plants. Wet the leaves down with a spray bottle, drop the lady bug onto your plant and quickly shut off any lights in the room. This is best done at night, because ladybugs have an instinctive tendency to fly toward any light source when preparing for hibernation.

Why Insecticides Are Impractical

There are several commercial sprays and dusts available that claim to prevent or control Asian Lady Beetles. These insecticides are impractical, because there is no way to get to areas where the ladybugs are congregating in mass, and fall weather puts the bug's physiological activity near zero, which make them less susceptible to insecticides. In order to kill ladybugs indoors, you would have to apply the spray to surfaces, such as counter-tops, where residual chemicals could be hazardous to your health.

A Note About Allergies & Bites

Although it is uncommon, Asian Lady Beetles can cause allergic reactions in some people. Symptoms include itchy eyes, sneezing, congestion and a runny nose. Asian Beetles do not carry disease and they do not have any toxins associated with their mouthparts. Occasionally they may pinch your skin when being handled, but they seldom break the skin. You may also feel a slight prick on your skin when handling the beetles. This is caused from small spurs on the beetle's hind legs which it uses to establish whether or not something is edible. Don't worry, you're not. In the unlikely event you become concerned over a pinch or a prick, wash the site with soap and water and apply an antiseptic.

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