MAINE, USA — It's official -- black fly season is here in Maine. The insects traditionally like to spend time in densely wooded areas and flowing bodies of water. 

"Black fly season is black fly season. And once they're out, they're out," said Jim Dill of the UMaine Cooperative Extension. 

Dill spends lots of time studying insects and has noticed a gradual difference in the population. Maine's cleaner bodies of water have created a better breeding ground for black flies. The insects like to breed in fresh, flowing bodies of water. 

That has lead to an increase in species, according to Dill. He says there are roughly 40 species in the state of Maine. 

This year's long winter has also had an impact on black flies. 

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"It was colder, longer -- and because of that, we've kind of concentrated the season," said Dill. 

That means that multiple types of species are out at the same time, which can make it seem like there are even more flying in the air. 

"Folks bought head-nets while we were up in the north country, and that's the first that's ever happened in the time I've been leading trips up to Baxter," said Seth Benz, who works with the Schoodic Institute. He spends time taking visitors to different parks in the state. 

"In the past 48 hours or so, they've been very plentiful," added Benz about the black flies he saw in Baxter State Park. 

Not every area in Maine experiences black flies the same way. 

Dave Enman, the president of DR Disc Golf, says this year hasn't been as bad as past years. DR Disc Golf is a disc golf course in Orrington that has 45 playable holes, which are all outdoors in heavily wooded areas. 

Even though Enman found that there are less black flies around, it does impact his businesses. He says that during black fly season, there's about a 50 percent decrease in disc golfers at his course. 

"It's just really hard to play when you're getting swarmed by black flies," said Enman. 

"I consider them the state bird, they're just tough little guys," added Enman.