Don't know about the earthworm, but for the ant it's like this: The ant itself might not feel pain but the ant colony as a whole does feel "pain", the reason f

Don't know about the earthworm, but for the ant it's like this: The ant itself might not feel pain but the ant colony as a whole does feel "pain", the reason for this is that an ant is the equivalent to a human cell. It doesn't feel pain by itself. To verify this, just find a big ant colony (with hundreds of ants above ground, doing their stuff) and then step on some ants and you will see them completely freak and try to find the attacker so that it doesn't cause any more "pain" the colony.