Lifting up piece of bark from a fallen tree I found this nest of ants. I don't know what the interaction was between the different ants when the bark was in place but once the bark was lifted there was quite a bit of activity. The large black carpenter ants came to where the small pale ants (I'm assuming Citronella ants judging from their odor) and would grab them. The small yellow ants, when not being harassed by the carpenter ants, were occupied in moving the cocoons to a safer area under another section of bark.