Nice - I've got a similar situation on my bedroom rack. For a while we had ants living in the house, but I think the Neps have done such a good job on them that they wiped out the local populations. Now I find ant trails on the outside walls leading into my racks through the windowsill or the ventilation holes in the foundation. :D
They're so much fun to watch! This also reminds me of a question - do you ever see ants start to get a little clumsy or disoriented while feeding on nectar? The ones at my house seem to. But the weirdest part - and I'm wondering if anyone else has seen this - is that the "drunken" ants are often rescued from precarious situations by their more sober sisters. An ant will be dangling dangerously from a pitcher's peristome only to grasp mandibles with a nestmate and be hauled back to solid ground. Sometimes, the really messed up ones will be carried off by the others. (Maybe there's some kind of drunk tank back at the nest?) I'd never heard of this level of altruism among ants - could it be that there's some sort of "Help me, I'm falling!" scent signal at work? I'm very curious to know if any of you have seen or heard of this.