Help! My Chihuahua keeps humping my Boston puppy!

Hi. I was wondering if anyone had any advise on how to stop my male Chihuahua from humping my 10 week old Boston Terrier puppy. He is neutered. I'm not sure what age he was neutered because we adopted him from a rescue. (he was already neutered when he came to the rescue) He just started this last night. He is driving me nuts and I'm sure her too. She goes to get spayed June, 3. Will he just stop on his own or is there something I can do?

Thanks for any advise you could give.

I think it's a dominance thing rather than a sexual thing! As your puppy is only 10 weeks old she won't be capeable of having a "Season" yet!!
He's probably trying to tell her "I'm top dog here!"
I would tell him off when he does it, as lets face it, it's not nice manners!
And i'm sure they will sort out a pecking order between themselves soon enough, make sure that you give you Chihuahua lots of attention as his nose is probably a bit out of joint, after all you didn't ask him if you could bring a puppy home!
hope this helps!