During this time of year when the weather is cooler, the multicolored Asian lady beetle, Harmonia axyridis, congregates on the south side of buildings and enters homes. The beetle does this because in their native China they inhabit tall cliffs to overwinter. Because Illinois does not have an abundance of tall cliffs, the next best thing is a building.

The multicolored Asian lady beetle is a native of Asia (hence the common name) and was introduced into the southeastern and southwestern portions of the United States to deal with aphids on pecan trees. It spread rapidly to other portions of the country. It is an arboreal (tree-dwelling) lady beetle, more so than the native species, and a very efficient predator of aphids and scales. In fact, this beetle has been responsible for regulating populations of the soybean aphid, which was introduced into Illinois about 2 years ago. Adults may also feed on ripening peaches, apples, grapes, and other fruit, creating shallow holes. This damage may be easily controlled with the use of common insecticides registered for fruit. Large numbers of beetles feeding on fruit may cause enough injury that the fruit is less appealing for consumption.

This lady beetle can be easily distinguished from other species of lady beetles by a pair of white, oval markings directly behind the head, which forms a black, M-shaped pattern. Adults are 1/4 inch long, 3/16 inch wide, and vary in color from yellow to deep orange (almost red). In addition, their bodies are usually (not always) covered with 19 black spots. The adults can live up to 3 years. Female beetles lay yellow, oval-shaped eggs in clusters on the underside of leaves.

The eggs hatch into larvae that are red-orange and black, shaped like an alligator. The larvae primarily feed on soft-bodied, plant-feeding insects, such as aphids, psyllids, and scales. They eventually undergo a pupal stage. The pupae can be seen attached to plant leaves. Adults emerge from pupae and start feeding on prey. The adults can be found on a wide variety of trees, including apple, maple, oak, pine, and popular. There may be multiple generations per year.

The multicolored Asian lady beetle is a nuisance pest because the adults tend to congregate and overwinter inside buildings in large numbers (literally giving meaning to the phrase “ladybug, ladybug fly away home”). They release a pheromone that attracts more beetles to the same area. Although they may bite (and they do), the beetle does not injure humans. Additionally, the beetle does not carry or transmit diseases. The beetle does not breed or reproduce indoors because it is primarily looking for a place to spend the winter. They are attracted to lights and light-colored buildings, especially the south side where it is warm. The beetles work their way into buildings through cracks and crevices. Dark-colored buildings are generally less attractive to the beetles.

Beetles can be prevented from entering homes by caulking or sealing cracks and crevices. Beetles that are already in the home can be removed by sweeping or vacuuming. Be sure to empty the vacuum bags afterward. Avoid killing the beetles. Simply release them outdoors beneath a shrub or tree away from the house. If the beetles are crushed, they emit a foul odor and leave a stain that can be difficult to remove. The dust produced from an accumulation of dead multi-colored Asian lady beetles behind wall voids may trigger allergies or asthma in people. Insecticides are not recommended for use indoors.

Homeowners who want to avoid dealing with overwintering beetles entering their homes can hire a professional pest-control company to treat points of entry on the building exterior with a pyrethroid-based insecticide. The treatments should be made in late September or early October, before the beetles enter the building to overwinter.

The beetle has been able to spread rapidly throughout portions of the United States because it was introduced into the country without its native natural enemies. However, beetle populations may decline as cosmopolitan natural enemies start attacking them.