Large numbers of Asian Lady Beetles showing up in homes
Beetles introduced in 1919 became house pest in 1990s
Lately, homeowners may have noticed a large number of Asian Lady Beetles, which can look similar to ladybugs, coming from seemingly nowhere to visit their homes.
"This year seemed worse," said Tim Schnakenberg, regional agronomy specialist for the University of Missouri Extension. "I can't explain why this fall is worse than most, but it tends to be a fall and spring issue. When we're transitioning from warm-to-cold or cold-to-warm, that's when they get active again. They're just looking for a warm place. When they start sensing the cold weather, they start moving to attics of houses, and if there's any opportunity for them to come into the house, they will, and next thing you know, they're coming in by the droves."
But, residents need not worry the beetles will take up permanent residence.
"The best thing they can do is seal the houses up," Schnakenberg said. "They may last a little bit longer, but eventually they will die. These are the non-native beetles that were actually introduced by entomologists in america by the USD in 1919."
It was originally for a good purpose, because the beetles provide great aphid control, but it got out of hand, Schnakenberg said.
"It took about 70 years, but they finally got to the number that they became a pest," he said. "In the garden, they're an outstanding aphid control measure, but their population started to grow exponentially in the 1990s, and the extension office started getting a lot of calls about them getting worse and worse.
"Its just a natural progression of a population. Usually its under the eaves of the house. You just have to seal up the house as best you can. Once they're in the house, you about have to just vacuum them up."
The beetle comes in a range of colors from beige to yellowish-orange to dark reddish-orange, with between 0-19 black spots on their body.
"I believe that's how entomologists tell them apart, by the number of dots on their backs," Schnakenberg said.
"They are very beneficial insects that feed on several pests of horticultural plants and crops. Adults can live up to three years. Asian Lady Beetles typically invade homes during October and November and congregate in dark, undisturbed locations such as wall voids or attics.
"When they become active in March or April, large numbers of them may be seen crawling on walls and ceilings inside the home. They do not sting, carry disease or bite. They have not been observed feeding on wood, cloth or stored food items. If handled, they will release a defensive chemical, which has a mild odor and may stain walls and fabrics."
Schnakenberg said no attempt should be made to kill the insects while they are passing the winter in wall voids or attics. Killing them without cleaning out all of the dead bodies would provide a food source for scavenger insects like larder beetles and carpet beetles. If these beetles are established, they are a bigger problem than either boxelder bugs or Asian Lady Beetles because they will infest stored products, fabrics and more.
While they may seem like a nuisance at the time, the tiny, colorful beetles can be helpful as predators of other insects.
"They are beneficial because both the immature larval and adult stages feed on aphids, mealy bugs, scales and other soft-bodied insects," said Mary Kroening, University of Missouri horticulturist.
In their native habitat, the insects overwinter in cliffs, so they seek out vertical surfaces such as the walls of light-colored homes that have a south or southwest exposure.
They gather in undisturbed areas such as attics and spaces within walls until March and April, when they move outside in search of food.
"Many homeowners get irritated due to the large numbers that can be present in their homes," Kroening said. "However, Asian Lady Beetles do not feed on wood, clothing or human food and they do not reproduce indoors during the winter.
To collect the beetles, use a vacuum cleaner or dustpan. If you do vacuum, change the bag soon afterward. Left in the bag, the beetles die and leave a permanent odor in the vacuum bag. Emptying the bag outdoors allows the insects to live and continue their role as predators."