The ants would be bigger, of course. Still be vermin, though, because of the vermin tokens.
You won't be able to make a civ hostile by default without those tags. Except ambusher; that makes their siege squads start out hidden in ambush mode, but doesn't make them immediately hostile.
If you really don't want them to come stealing babies or trinkets, you can try giving them ethics that clash with everybody. They will declare wars every once in a while, but wars won't be the default state necessarily, and wars do end. You could also make them [CRAZED] in which case they will immediately go about killing everything that isn't the same species. That will include pack animals, and if they aren't at war with you and won't send thieves or snatchers, then the only reason they will show up is to trade. They will have to use pack animals, and they will immediately kill their pack animals if crazed. As soon as any member of a trade caravan dies, including the pack animals, the caravan will turn around and go home. If they're crazed they will also attack their own war animals or zombies. So that's not really an option.
I would suggest making them baby snatchers or thieves. Let them sneak about, raising zombies as they go, and then haul children off to turn into zombie stock later. (No way to make them kill what they take, but if they have zombies around the zombie will probably kill the kid.)