They came down from the sky one balmy, sunny morning last week. Thousands of orange Asian Lady Beetles rained onto campus like locusts, infesting classrooms, dorm rooms, and even preying on unsuspecting students who mistook them for the kinder, friendlier ladybug.
The beetles, which closely resemble ladybugs but have a distinctive orange shell instead of the ladybug's dark red, emerge every October for about a week, seeking to find a place to hibernate for the winter, according to May Berenbaum, an entomologist at University of Illinois, Urbana-Champaign.
"In Asia, they like to over-winter in crevices, in vertical rock spaces, and cliffs. We don't have a lot of cliffs. But what about a building? A building is the closest approximation to the cliffs. And it's very easy for them to get into those crevices," Berenbaum said.
The beetles, which are not native to the United States, were introduced into this country about 20 years ago in order to control the population of orchard aphids that were infesting pecan trees in the Southeast. But the beetles spread rapidly and now inhabit Florida, the Northeast, Ohio, Illinois, and the Mid-Atlantic.
"They eat anything that's slow enough and soft for them to catch. They have a broad range of eating habits, and are displacing some of our native ladybugs. Any place where they are in abundance, it's hard to find our native ladybugs," Berenbaum said.
The beetles' strong jaws make them especially well suited as insect predators, said Berenbaum, who believes that some beetles are interested in finding out whether people make a tasty treat.
"My impression is that based on the way they live their lifestyle, they bite you just to see if you're edible. If you grab them, they bite you for defensive mechanism. They have strong mandibles and it hurts," Berenbaum said.
First-year graduate student Susan Ferrari was a victim of a particularly aggressive Asian Lady Beetle, which she mistook for the gentler, less vicious ladybug. "They bite your eyes," she said. "It hurts a lot."
According to Martin Feder, a professor in the department of organismal biology and anatomy, the recent heat wave may have caused the beetles to come out for one last gasp of activity before retiring for the winter.
"It's my impression that the unusually high temperatures are allowing them to be very active," Feder said.
First-year in the College David Meisner has encountered several problems with the beetles but said that the infestation can be beneficial.
"In one of my classes, the whole ceiling was covered with them," Meisner said. "During class they were a distraction, but they also keep you awake because they bite you."
The U.S. growing population of the beetles makes Berenbaum worry about the harm being done to native species. "They're doing incalculable damage to soft-bodied insects that aren't doing damage to anybody," she said.
The beetles have even displaced many native ladybug species, causing concern in the community of entomologists, according to experts.
"If they haven't displaced all, [they have displaced] certainly a lot of them. People who keep track of these sorts of things are kind of alarmed. They're taking over the good guys," Berenbaum said.
Berenbaum fears that the beetles' aggressive behavior is reversing the historically positive attitude that humans have had for ladybugs.
"I guess they're the bad apples in the ladybug bowl," Berenbaum said. "These are predacious ladybugs that everyone up to this point in history have had affection for. Farmers really like them. They're completely ruining the image of ladybugsthey bite and they smell bad."