Researchers at the University of Maine said the webs of some browntail moth caterpillars have been spotted in Bangor, Orono and Old Town.
The forest caterpillars attack trees but also have hairs that cause a rash if they come in contact with human skin.
After not being around for many years, browntail moth caterpillars had an outbreak in 2015 and researchers are looking into why they're continuing to spread to other parts of Maine.
"So if you live in Bangor but you have a beautiful camp down in Damariscotta and you're bringing your camper back and forth, parking under some of these trees, we think that you're potentially bringing some of the caterpillars north," said Karla Boyd, UMaine graduate student, and research assistant.
Researchers said the public should mow their lawns on wet days and cover their skin when hiking to try to avoid exposure to their hairs.
The bugs are brown, make small nests and have white splotches and two orange dots on them.