For several years we have had to endure a home invasion of ladybugs that are determined to make themselves bothersome houseguests, and this year is particularly bad. They are beneficial creatures, feeding on other bugs that damage farm crops. But indoors they drive you nuts buzzing around lights, dive bombing into drinks, and smelling bad.
There are many species of ladybugs, some native to the U.S. All are beneficial predators that consume aphids, scale insects, and many other pests that injure plants in gardens, landscapes, and farms. The beetle giving us indoor problems is the multicolored Asian lady beetle, Harmonia axyridis, a foreign import. You can tell it from other ladybugs by looking for a black “W” around the head area. It got here through a number of accidental and planned releases mostly in the 1970s to control insect pests in fruit and nut trees. In their native habitat, large numbers of these beetles overwinter in cracks and crevices within cliff faces. Unfortunately, we don’t have enough cliffs to go around, so they seek cracks in and around buildings.
They tend to orient toward light-colored objects, such as white buildings. Large numbers collect on outside walls warmed by the sun, especially on the south and southwest facing walls. When one ladybug lands, others soon follow, and research suggests that this aggregation behavior may involve chemical or visual cues.
Asian lady beetles seek protected sites such as under siding, roof shingles, firewood stacks, or leaf litter. Others slip through cracks and crevices and come indoors, where they may cluster together in the corners of porches, attics, or other dark, undisturbed areas. They also invade living spaces in response to the warm interior temperatures. On warm sunny days during the winter, they tend to move about and fly within living spaces and will readily fly to windows and lights.
Besides buzzing around the house, the Asian ladybug also cause stain and odor problems. When disturbed, they defend themselves by exuding a yellow-orange body fluid, which is actually bug blood. This defense mechanism is termed reflex bleeding, and it has a foul odor and can permanently stain walls, drapes, or carpeting. Another aggravation is their biting. Ladybugs are not aggressive toward humans but may check out an unfamiliar surface by nibbling it. Some individuals report an allergic reaction to bites, and also causing inhalant allergies.
Good or bad, Asian ladybugs are here to stay, so all you can do is figure out how to deal with them. Information on how to do that can be obtained at your local County Extension Office or do an internet search for ladybug traps. Commercial traps are also available.