Extension Educator, Horticulture
They're back! Actually they never really left. Asian lady beetles have just been preoccupied with eating soybean aphids all summer. As their food source declines in the fields, they will be searching for a new fast food joint and a winter retreat.
Lady beetles are usually considered good bugs. They eat lots of pest species like aphids and scale. Even though there are several species of lady beetles in Illinois, one is giving the rest a bad name. Multicolored Asian lady beetles like to spend the winter in our homes, they occasionally bite and they can eat apples, grapes and raspberries.
Asian lady beetles like to taste things including us. They can and do bite. Although they have no venom, the bite hurts and can leave a red mark.
The multicolored Asian lady beetles are one-fourth inch long and are the VW bug dome shape. They usually have orange wingcovers with 19 black spots. No need to count the spots. Their multicolored name comes from the variety of color possibilities ranging from tan to red and the spots may be very small to absent, to large and obvious. If you get up close and personal, you can also see four black spots behind the head that forms a "W" when viewed from the front or an "M" when viewed from behind.
Both the young larva and the adults feed on a wide range of insects. Multicolored Asian ladybeetles are very good at controlling aphids on trees and shrubs. They were first imported into Georgia to control the pecan aphid.
In their native areas in Asia the multicolored Asian lady beetles spend the winter in cracks and crevices of cliffs. Cliffs are tough to find in central Illinois so what is the next best upright thing around? Our homes of course. In the fall they start their migration flights. They are particularly attracted to light colored structures with sunny exposures. There they congregate in large herds on the sides of buildings. They wander around and enter buildings through cracks between siding, around windows, around roof flashing and overhangs. Or they may fly through doors as people go in and out.
If there is no heating in the building, the beetles just snuggle together and wait for spring. In heated buildings especially on bright sunny days they may start flying around trying to escape. These eventually die on the windowsill.
The good news is ladybugs don't reproduce or feed while they are indoors. Controlling these insects indoors consists of vacuuming (be sure to empty the bag afterwards) or your best scoop and toss outside method. Don't smash them on furniture or drapes. If crushed, the beetles will emit a foul odor and leave a stain. Soon they will all have gone outside one way or the other.
Insecticide sprays are likely to have little to no effect on hard-shelled insects that are not feeding unless you get lucky and happen to drown a few. You may get some satisfaction out of spraying insecticidal soap every couple days outdoors on congregation walls. Preventing ladybeetles from entering buildings is the best control measure. Caulking cracks and crevices around windows, along the foundation and around doors will help reduce the numbers that can make their way indoors in the fall.
Commercially available indoor light traps can be effective. They are effective only at night as beetles are attracted to the light and best used in rooms without other lights.
Remember ladybugs are actually good bugs outside. Repeat this over and over to yourself as you are scooping them up from your windowsills. U of I has a nice fact sheet on these critters at http://www.ipm.uiuc.edu/hyg/insects/asian_lady_beetle/