As residents kill those they find crawling around in their kitchens and bathtubs, 95 percent of them remain alive and well back home in the nest, they say.
And there's even more problems this year, one researchers said.
"It seems the season for them is longer now," Grzesiek Buczkowski, an urban entomologist at Purdue University in West Lafayette, Ind., told The Kansas City (Mo.) Star.
Professionals "would usually only treat in spring and summer. Now they're treating for them in winter. We are hearing from exterminators that they are getting more calls, and at really odd times, like the middle of January," he said.
The odorous house ant, sometimes called the sweet ant, emits an order like rancid coconut suntan lotion if crushed, a defense mechanism to alert other ants that something is amiss.
Cities and suburbs have become a favored habitat for the ants, Buczkowski said, because there are fewer natural competitors for food, better access to food and better nesting sites.
"Even if you get rid of them one year, they'll probably show up again next year," said Buczkowski, who has ants every year in his own suburban home. "It's a losing battle."