Once again, Asian ladybird beetles have descended onto the ISU campus, finding their way into everything.

The beetles usually don’t cause any harm — but they can be annoying.

“They’re probably more of a nuisance than mosquitoes when we work,” said John Armstrong, who has been working on the construction at Morrill Hall.

“They cling, then they bite, and you stop what you’re doing to slap them.”

Although the beetles do bite, they’re unable to break skin and don’t carry diseases, said Matt O’Neal, assistant professor of entomology.

“They’re getting into the apartment just by crawling in on us,” said Justin Paisley, sophomore in chemical engineering.

People who don’t want to share their houses with the little visitors don’t have many options.

Short of completely sealing a house, it’s hard to keep the beetles out.

Traps with black lights that the beetles fly toward are available, but …

“I haven’t seen anything to suggest these are useful,” O’Neal said.

Research is being done on products to attract the beetles away from people, he said, but they aren’t commercially available.

The bugs also have a distinctive smell.

“They have a defensive chemical in them,” he said.

“The smell is to ward off predators.”

The beetles are native to China and have been introduced to the United States multiple times dating back to the 1920s, O’Neal said.

Some introductions, he said, were intentional.

“The most recent introduction was in the early ’90s or late ’80s in the Southeast for a bio-control program against an aphid species,” he said.

There is no way of knowing if the beetles in Iowa are from that release or if they came with a shipment of goods from China, he said. The beetles never established themselves in the Southeast after they were released.

During the summer, the beetles live in soybean fields, feeding on many different things, including aphids and other ladybird beetle species.

O’Neal said the beetles can produce two or three generations during the summer.

“We had a cold spell, and that triggers them to start looking for some place to spend the winter,” he said.

In China, the beetles look for damp crevices in cliffs or the south side of a mountain where it’s sunny and warm to spend the winter, he said.

In Iowa, the beetles use buildings instead.

O’Neal said there may not be as many beetles to keep out of your house this fall.

“We saw fewer aphids in the soybeans,” he said, which means there’s less food for the beetles.

Last year, there were 10,000 aphids per soybean plant. This year, there were about 100 aphids per plant, he said.

“I think there are less of [the beetles] but they’re just as annoying,” Paisley said.

“If we get a couple cool nights, another hard frost or two, that will keep them from flying around,” O’Neal said.

The beetles will continue to crawl around inside buildings for about a week, searching for a hiding space.

“In April, they will start coming out again,” O’Neal said.