Awesome pictures Larry! What are you using to get such good close-ups?
I believe your ant is Linepithema humile, which is a terribly invasive species and is sadly causing great harm to the ecosystems. The biggest reason why these ants are so terribly invasive is because of how genetically similar the entire population is. They are so similar that they form "super colonies" that cover vast areas of land all with the same colony scent. (there use to be only 1 super colony in the u.s. but, recently super colonies have begun to break apart into more then one colony. (that is a good thing.)