Under attack

I noticed a little caterpillar on a path and went inside to get my camera. When I returned only a minute or two later the caterpillar was under attack by ants. It was wriggling rigorously and trying to escape but the ants were persistent and as I watched reinforcements arrived. It's amazing how quickly the message was passed along that there was a potential food source. As far as I could tell the caterpillar wasn't injured but maybe the ants knew more than I did.

 In the two photos below the caterpillar is still very active and so are the ants. Presumably the ants are nipping or stinging the caterpillar.