A shirtless barefoot nut with a criminal history chomped down on the arm of a female cop as police tried to arrest him in the Flatiron District on Thursday afternoon, law-enforcement sources told The Post.

Crazed suspect Lonnie Payne, 45, initially strolled up to the officer and her female partner on foot patrol in Manhattan and sneered, “Bitch, what’s so funny” and spit at them around 1:30 p.m., sources said.

As the two female officers tried to slap handcuffs on the menace, he allegedly sunk his teeth into one of them and head-butted the other, sending her to the ground, police said.

Photos from the scene show the bitten cop holding her right arm in pain with an apparent teeth mark near her elbow, while other snaps depict the suspect in handcuffs with a wild look on his face.

Both attacked officers were treated at an area hospital, police said.

“The police woman was just standing by the day crew, and they were doing nothing, they didn’t say anything to him, but he was a little bit cuckoo,” a witness said.

“He was talking and barefoot and without a top, and then all of sudden, he went to them,” the onlooker said of the suspect — who was only wearing a pair of grungy dark sweat pants that were rolled up to his knees.

Payne is facing two counts each of assault on a police officer, resisting arrest and harassment, according to the NYPD.

He has at least 11 past charges lodged against him as early as August 2008 and as recently as last year, according to sources.

The previous charges include assault, criminal sex act, grand larceny, harassment, resisting arrest, and obstructing emergency medical services in either Manhattan or Brooklyn, sources said.

In one instance, he allegedly exposed his penis on a downtown R train and pushed a victim toward his crotch in 2021, according to sources.

Payne has a history of mental health problems that have been on officials’ radar since at least 2021, sources said.

He was arraigned Friday in the attack on the cops and pleaded not guilty, according to court records. Bail was set at $25,000, records show.

His most recent address according to cops is the 30th Street Men’s Intake Center – a male-only Manhattan homeless shelter.

Thursday’s attack is among a disturbing trend in the Big Apple in which assaults on city law enforcement has jumped 63% compared to six years ago, according to data obtained by The Post in May.

The stats show there were 970 assaults on uniformed cops in the city as of May of this year, which is up from the 595 officers who were attacked at the same point in 2019.

Law enforcement experts have blamed lax criminal justice policies for creating an atmosphere where brutes don’t fear going after cops.

“You have a criminal justice system that’s a revolving door and people are getting arrested 40, 50, 60 times,” said Joseph Giacalone, a retired NYPD sergeant and adjunct professor at Penn State University-Lehigh Valley, previously to The Post.

“The cops are dealing with people out on the streets who are really bad.

“I think people have just lost respect for the NYPD,” he added.