The sequence in which one ant after another carries the poison down to the queen so she can synthesize an antidote--each ant dying in its turn and infecting the next, who goes as far as it can before it dies, and so on--is the benchmark of alien intelligence at work for me, in a lot of ways.

Yes. I was also very struck by the scene in which the ants retrieve and lay out their dead, killed in the destruction of the solar reflectors: considered by itself, it's more evidence of their intelligence and communality, but it also chimes in contrast to the cavalier treatment of the human family who died in the same poison shower, stumbling through it for help that never came—left lying where they fell, covered in the Crayola-yellow mire they didn't even realize was killing them until it was too late. I don't know whether the ants are the "good guys" in this story, but the humans definitely aren't.