Washington-area residents – including many in dorms across the campus – have been enduring a foreign invasion in recent weeks, as multicolored Asian lady beetles make their way into homes and buildings to hibernate for the winter.
As many as eight beetle infestations have been reported in student housing, said Christine Garcia, Resident Life’s Urban Biology Manager, and many more are still crawling along windowsills and trapped between screens as they make a futile attempt to retreat from the cold. Garcia has directed crews to vacuum the pests away rather than use pesticides, she said.
“We would rather keep insects and other pests out of our buildings rather than use pesticides after they’ve gotten in,” Garcia said. Crews have also been busy using caulk to plug vulnerable entry points for the bugs and replace damaged screens. “One window in the stairwell in our building I noticed had about a dozen ladybugs on it,” said sophomore architecture major Vanessa Nwankwo, who lives in La Plata Hall.
Although the beetles resemble ladybugs and have colors that range from yellow-orange to red, their behaviors are different from those of American lady bugs, said entomology professor Michael Raupp. The beetles are often called Halloween lady beetles because they enter homes in droves beginning around the third week of October.
They are distinguished by black spots forming an “m” or “w” in the area directly behind the head, and would normally seek refuge in crevices or cracks on rocky cliffs in their native Japan. But since their introduction in America, the beetles have grown attracted to light-colored walls, gaps in windows, unscreened vents and crevices on the sides of buildings.
“The ones we have here have a different overwintering habit” than those in Japan, Raupp said. “It’s not part of their evolved behavior to come inside.”
Although the beetles may be considered pests during their short time attempting to hibernate, they are generally considered beneficial bugs, and were introduced in 1916 because of their voracious appetite for the plant-eating aphids that plague pecan and apple groves through the summer and fall.
They became more numerous in this area when the U.S. Agriculture Department began intentionally releasing Asian lady beetles from the 1960s to the 1990s in states from Washington to Maryland for biological pest control. The species is now prevalent on the East Coast and in Canada.
Raupp said the species is relatively harmless and said lady beetle bites elicit no more than a tickle and do not break the skin. Garcia said, however, that those allergic to insects may react to a protein in the lady beetle’s outer shell.
“As dead insect bodies begin to break down, some of these proteins may become airborne causing rashes or respiratory reactions in sensitive individuals,” she said. “Ordinarily, this type of reaction only occurs where there are very high numbers of dead insects.”
Raupp said, however, that specific allergies to lady beetles were probably rare.
They can get a bit stinky and messy, however. When frightened, lady beetles are known to release a noxious yellow fluid from the leg joints as a defense mechanism, accompanied by an unpleasant odor. This reflex bleeding can leave stains on furniture, walls and fabrics.
But “no property damage attributable to Asian lady beetles has been brought to my attention to date,” Garcia said.
Raupp said the lady beetles could generate dollar signs for those who don’t mind collecting the live beetles for safekeeping over the winter. The beetles can be “put into refrigerators or holding chambers before they’re sold to farmers [or] homeowners.”
Contact reporter Allison Stice at newsdesk@dbk.umd.edu.
