My boyfriend stares a lot at other women.

Have you talked to him about it?

I pointed it out to him a few weeks ago, but didn't have a discussion about it. Just briefly says he does it. Didn't want to make a big fuss, because it didn't bother me much at the time. He says it's a natural thing for guys to do, I did agree.
But it has gotten to that point now where it does upset me.
Will he take it on board if I do talk to him about it?
I heard if guys proper stare at women, they will ultimately cheat. I think that is what worries me.

Yes he's being much too obvious, he should do what I do when I'm in the supermarket and quietly move an item on the shelves to one side so I can watch the cashout women on the other side through the spyhole

First of all, if it upsets you then you should talk about it until it is resolved. Communication is important in a relationship and hopeful you boyfriend will care enough to resolve this so that you are comfortable.

I am careful not to stare at other women when I am with my girlfriend just out of respect for her (actually I don't stare at women that much anyway) but I would hate the idea of my girlfriend feeling bad when I am with her.

There is a difference between a glance and a stare. As a man, I don't think that staring at women for more than a second is a necessary part of being a man especially when we are with our girlfriends. If this is making you uncomfortable you should definitely tell him how this makes you feel. When my girlfriend tells me things that make her uncomfortable, I listen. This is important in a relationship.

The Girl always says that if i ever stop flirting, she's gonna check for a pulse and call the EMTs.

You're right, thank you.
I'll talk to him about it the next time I see him.
It usually doesn't bother me when he does it, but I feel it has gotten out of hand.
Like you said - if a man has a girlfriend and says he loves her - why stare at other women for long periods of time?
I know it's natural and girls do it too, but there's a difference between glancing and blatant staring.

I once got in trouble with a new date about 10 years ago, we agreed to meet on a park bench and started chatting alright, but then it started to rain so we moved to a nearby bus shelter.
Among the small group of passengers waiting for the bus was a lady who started chatting me up and I politely replied rather than just ignore her.
But my date didn't like it, she said "I don't think we're well suited, goodbye", and walked off in a huff!
Then the bus pulled in and the group got on, including the lady who'd been chatting me up, and I was left there on my own thinking "Huh? what happened?"

To be fair, that is a little bad that she did that. You were just being polite. There's nothing wrong with being polite. You weren't in the wrong.
It's just if a guy is with a girl and he blatantly stares or flirts with other girls whilst he's with his date - that is a bad sign, right? Or am I just being touchy?

YES! You should be concerned.

He is being very immature and inconsiderate of your feelings. Very young boys do this. How old is he?

This habit does not get better. Plus, he will grow up to be a dirty old man.

(I am talking about turning around or moving in order to look at another woman that passes by. If the girl is right in front of both of you, then it is not an issue.)

He's 21.
He always keeps his mobile on silent and never texts when I'm around him too. Tries to hide his screen when he does. He checks it only when I'm not there. Is this a bad sign too?

You and Wally would get along great.

He's young and immature - probably not ready for a real relationship.

He's just a kid.

My wife and I have a simple agreement that haw always worked well. She knows that when I see an attractive woman I am going to look. She allows the first look. She might sometimes allow me a second quick glance. But anything more than that and she gets to punch me in the arm at which point I normally turn toward her and she plops a kiss on my lips. Just our way of reminding each of us who we've given our hearts to. Works for us. (And quite frankly, I almost never take more than one look. The kiss is nice, but my wife can hit pretty hard.)

How would he react if you stared at other men in front of him?
You should definitely talk. I also had this situation once, and my bf just didn't realize how much it hurt me. But he says I am important to him, so he's working on his "looking" habits.

Hey RedDragonfly, he ought to get a secret "lapel camera" so he can secretly video women without them or you knowing, then download them to his computer when he's alone to leer at in private..

that just sounds odd. How do women react to the staring?

Looking and casual flirting are one thing - long periods of staring sounds abnormal (could just be a matter of perception on your part - we don't know what you mean by long periods of time).

Agreeing with ehBeth here -

It's normal to look at humans in the first place, if you like watching humans, for a lot of reasons. Liking looking at the people whose gender you are particularly attracted to is even more fun. (I caught myself looking at the guy in the Dos Equis ad just today..) I don't want anyone stopping me from doing that. How dare they?

Some of us are flirts, some aren't, but a great deal of flirtation is just playful and not to be taken seriously. One learns to tell the difference.

Staring and staring isn't something I take as playful/non serious. Invasive would be the word I'd pick first.

Is that what you do?

Well I've got a small camera and have thought of hanging it round my neck and going to secretly film the woman in the chip shop, but disguising it would be a problem, I suppose I could cut a small hole in the front of an old jacket for the lens to peer through, but it'd probably mask the auto-focus sensor..