The multicolored Asian lady beetle, Harmonia axyridis, a native of Asia was introduced into the southeastern and southwestern portions of USA to deal with aphids on pecan trees. However, it spread rapidly to other portions of the US. During the fall and early winter when the weather is cooler, the multicolored Asian lady beetle starts congregating on the south side of buildings and enter homes. The beetle does this because in their homeland of China they inhabit tall cliffs to over winter. There are very few tall cliffs in Illinois, so the next best thing is your home.

The multicolored Asian lady beetle is a nuisance pest because the adults tend to congregate and over winter inside buildings in large numbers. The beetles release a pheromone that attracts more beetles to the same area. Although
it may bite, it does not injure humans nor can it breed or reproduce indoors. They are attracted to lights and light-colored buildings, especially the south side where it is warm. They then work their way into buildings through cracks and crevices. Dark colored buildings generally have fewer problems with beetles.

Beetles can be prevented from entering homes by caulking or sealing cracks and crevices. Beetles already in homes can be physically removed by vacuuming. Be sure to empty the vacuum bags afterward.
Do not kill the beetles. If crushed, the beetles will emit a foul odor and leave a stain. The dust produced from an accumulation of dead multicolored Asian lady beetles behind wall voids may trigger allergies or asthma in people. Insecticides are not recommended for use indoors. Homeowners that want to avoid dealing with over wintering beetles  entering their homes can hire a professional pest control company to treat the points of entry on the building exterior with a residual insecticide. The treatments need to be made in late September or early October before the beetles enter the building to over winter. The beetle has been able to spread rapidly throughout portions of the USA because it was introduced into the country without its native natural enemies. However, populations may decline as cosmopolitan natural enemies start attacking them. For example, studies in North Carolina have demonstrated that up to 25% of the beetle populations are being parasitized by a tachinid fly.