PORTLAND, Maine (AP) Maine’s season for black flies appears to be taking up more of the year due to factors including cleaner water and climate change.

Black flies are small insects, some of which feed on human blood and bedevil outdoor adventure seekers in the state. Jim Dill, a pest management specialist at University of Maine Cooperative Extension, told the Bangor Daily News that a few decades ago the Maine season for black flies was from the end of May into the first weeks of June and then they would die off.

Experts said that doesn’t appear to be the case anymore, and the season now lasts for the entirety of the summer. One reason is because the flies need fresh water to reproduce, and decades of environmental protection laws have provided them with that, the Bangor Daily News reported.

Dill said the season now lasts from the beginning of pleasant weather through the first frost of the year. Different species are active at different times of the summer, he said.