7 year old dog and a new 11 week pup, what is good and bad behavior?

I have a 7 year old staffy and a 11 week old chihuahua, my staffy seems resistant to get along with my puppy chihuahua. The staffy has tolerated the chihuahua and apart from one incident were the chihuahua got harmed when my staffy tryed to warn her away from her chew bone, theres been no aggression. Recently though the staffy had started growling at my new puppy. Is this just a warning or could it lead to aggression? Her stance around my chihuahua is ridged, ears high stood tail wagging sometimes and the occasional heckle. My staffy hasnt had much socializing whilst growing up apart from with the cat. The chihuahua is full of life and always wants to pester my staffy, the puppy will jump up at the staffies face and bite the side of her face and try and bite the staffies ears, when this happens the staffy shows now heckles or aggression but when things get slightly to lively we tend to cool it down and both dogs go for a rest in there beds. My staffy doesnt really know how to play... she wont do the regular doggy play stance of head down and bum in the air she just stands firm to the puppy with pricked up ears... What is the course of action to take with a older dog and a new puppy???

To introduce them properly, you first have to stop the growling by your staffy. When you see him start to lower his head or hear a small growl, thats when you correct Him. Be consistent and then when the growling has subsided, pick up the other dog and introducing the behind to staffy nose. This is how they get comfortable with each other

I would be very careful, as one bite from your staff will very likely kill your puppy,the trouble with pup's they never know when to give in, certainly don't leave them alone together, and monitor the play, before play gets out of hand. I am not keen by the sound of the stance, as it sounds like dominance, and as you know a staff will go quickly and lock on, so be very careful.