old cat denys existence of new cat

Hi. I just adopted an 11 month old female. I have a 3.5 year old male brown tabby. The first day I kept them separate, but then I let them out and introduced them. My male is an indoor/outdoor cat and I am keeping the new one indoor. She seems fine with that. She has taken to her new home fine. She is eating, playing and just seems great. She is in love with my male cat and follows him around trying to play.
   
He on the other hand seems curious at times and then totally annoyed at other times. He will hiss at her and swipe if she takes a playful swipe. I don't get the feeling he wants to cause her harm. He just doesn't want anything to do with her.
   
I understand all of this seems fairly normal.
   
My concern is that he goes outside constantly now. He has always been fairly outdoor obsessed and the meowing doesn't relent until the door opens. I am afraid that he just may not come home one of these days.
   
I have been doing everything sites say to do with treats and stuff, but he is a fickle boy. It hasn't even been a week yet, but i am just concerned.

it is possible that your older male maybe feeling a little alienated from home, but unlikely, most introductions between a kitten and an adult is successful some just take longer than others, of course no owner wants their cats just to tolerate each other to a point, you want them to be best of friends, the problem is similar to what ive experienced in some ways, i have a male, recently spayed at 7 years, he has 3 sons, around 7 months old now, but you need to think like a cat, he dosnt associate family or kids, to him the three kittens are just more intruders to what he thought was safe territory, but your male sounds like a good cat, he isnt really hurting the kittens and he isnt running around pissing on everything in frustration, but the kittens want to play, with everything, including jumping all over him, my older boy dosnt tolerate it eaither, hell give them a big slap too, do they learn to leave him alone, maybe, for a few minutes and then... as your kitten grows up she will stop hassling you male, is your male spayed? if he isnt he may start disappearing for weeks on end, you should get him fixed or if your planning on breeding them then you should let them do their thing until it settles, introduced couple like this can take many years before breeding though, if youve already had him fixed then dont worry too much, it is rare for a spayed male to leave home and not come back, alternatively you could look at building an enclosed outside cat run, like a conservatory with chicken wire, then they can have the best of both worlds in and out, but not away