Why are there lady bugs on my windowsill?

Lady bugs are making their spring appearance around and in the home now that the weather is warming.

Increasing sunlight and warmer temperatures wake up hibernating insects. Photo credit: ardelfin, Morguefile
Increasing sunlight and warmer temperatures wake up hibernating insects. Photo credit: ardelfin, Morguefile

On days where the wind is calm and it is sunny, it is not uncommon to see “lady bugs” or more correctly, the Multi-colored Asian Lady beetle gathering on windowsills or a warm sunny wall (even on cold winter days). They begin to emerge in late winter and early spring when days grow longer. If sufficient warmth is generated on the sunny side a house or other buildings, the beetles will venture outside and onto the siding. When the temperature of the wall or siding nears 50 degrees Fahrenheit, beetles wake up and begin crawling around. Some (or many) might even come inside the house where warmer temperatures attract them. This is also true with cluster flies, western conifer seed bug and boxelder bugs.

Lady beetles feed on aphids and other soft-bodied insect plant pests. Both the adults and the immature multi-colored Asian lady beetle kill large numbers of these plant pests, especially aphids. This beneficial insect helps to control plant damaging pests without the use of pesticides. If you find large numbers of the inside your home or on the outside of your house then they become a pest insect themselves.

To clean and contain the insect without crushing them, you may want to try using a vacuum cleaner with a stocking over the end to collect and contain the insect. Try to avoid crushing the beetles, because they can release a yellowish fluid with a faint foul odor that can stain wallpaper and fabrics. Other steps you can take are to seal off cracks and crevasses by caulking around windows, doors and trim both outside and in to prevent access to your home for hibernation.

For more information about natural resources or invasive organisms contact me, Beth Clawson, MSU Extension Educator. To learn more about invasive organisms and invasive aquatic plants contact Michigan State University Extension Natural Resources educators who are working across Michigan to provide aquatic invasive species educational programming and assistance.

Did you find this article useful?