Asian Lady Beetles: The Most Helpful Insect Invaders

First-year public health major Tyler Watkins-Roden said they thought it was cute when a lady beetle flew past their ear Oct. 29. However, their opinion changed as, one-by-one, more beetles landed on their arm and bit them, eliciting tiny pinpricks of pain.

“I would have one attached to my skin, swat it off, and maybe three minutes later, there would be another one,” Watkins-Roden said. “So they were kind of infrequent, and they wouldn’t group up, thank God.” 

Multicolored Asian lady beetles, an invasive species of ladybug native to Southeastern Asia, have become more prevalent indoors in recent weeks due to the onset of cooler temperatures.  They can be identified by distinct “M”-shaped white patches on their heads. 

School of Environmental Sustainability Professor Reuben Keller, whose research focuses on invasive species, said an uptick in Asian lady beetles occurs every year during late autumn.

Asian lady beetles enter buildings through small crevices and openings, such as cracks in the corners of windows and door frames, in search of warm places to hibernate over the winter.

Keller said large congregations of beetles can also be found on outer building walls facing south, which are typically warmer.

“They’re coming into my house,” Keller said. “I remove two or three every day at the moment. They seem to be pretty skillful at finding ways in. Luckily, they’re not particularly good flyers, and they tend to stay still when you try to catch them, so it’s easy to grab them and throw them outside.”

Unlike Keller, Watkins-Roden hasn’t seen any Asian lady beetles in their dorm on the fourth floor of Simpson Hall. For the most part, she has only seen individuals or pairs of beetles on the outside doors and windows of classroom buildings.

“There was one in Mundelein, before the one in Dumbach, where it almost followed me into the elevator,” Watkins-Roden said. “I was like, ‘Oh my gosh.’ It didn’t get in, thank goodness.”

Multicolored Asian lady beetles can be deep orange, red, yellow, black or mottled, with deep orange being the most common color, according to biology Professor Martin Berg, an entomologist whose research focuses on aquatic insects. They can be identified by distinct white or beige patches on their heads.

Keller said the beetles don’t cause major damage to buildings. However, they have a mild bite and are capable of releasing a foul-smelling substance from their hind legs when threatened.  If they’re squashed against a surface such as a wall or table, this substance leaves a difficult to remove stain, making them a nuisance but not a threat to households.

“They don’t carry any diseases,” Keller said. “They don’t chew through the walls or anything — they’re not like termites or anything like that. They’re always hanging around these buildings because they’re warm, and if they get an opportunity to get inside then they go inside because it’s warmer.”

Keller said the multicolored Asian lady beetle was introduced to the U.S. by the government during the 1970s and 1980s to reduce the populations of aphids and other pest species and reduce the amount of pesticides and insecticides farmers must use to protect their crops.

These government efforts reportedly failed, but a population was discovered in the late 1980s and spread throughout the U.S., according to the University of Illinois College of Agricultural, Consumer and Environmental Sciences website.

Keller said the use of lady beetles in agriculture is much cheaper than using pesticides. Also, eliminating pesticides reduces the amount of chemical runoff from soil, minimizing the contamination of nearby rivers and streams.

Berg said Asian lady beetles, one of 12 ladybug species in Illinois, are far more beneficial to humans than they are harmful. However, they’ve had detrimental ecological effects, which is why they’re considered invasive.

The beetles secrete their foul-smelling chemical when eaten by predators, which deters them from hunting additional beetles. A lack of predation has allowed U.S populations of Asian lady beetles to grow exponentially, leading to “too much of a good thing,” according to Berg.

For this reason, Berg said Asian lady beetles are responsible for declines in populations of several native species of lady beetles, including the familiar red and black seven-spotted ladybug. He said their larger populations and larger body sizes usually allow them to outcompete their native counterparts. 

Despite the loss of biodiversity Asian lady beetles cause, Berg said it’s usually not in a farmer’s best interest to kill them because the existence of both invasive and native lady beetle species is considered essential for pest control. 

“The problem is they’re very effective predators — the invasive and the native ones as well,” Berg said. “But let’s say a disease comes in and kills all the invasive ones. If they’ve already eliminated the native ones, people in agriculture are going to have a problem.”

Watkins-Roden said they avoided killing the lady beetles that landed on them since the outdoors is their natural environment and they only infiltrate buildings seeking warmth.

“I think the bug in Mundelein was already on my arm,” Watkins-Roden said. “If it was inside, unfortunately, I think out of the startled kind of ‘oh gosh, there’s a bug inside,’ it would probably end up dead, but I would prefer to just relocate the bug.”