Phase IV! I found it on DVD maybe...three years ago, and I've never regretted it. The first time I saw it was on TV in Australia, and its horror might have stemmed at least partially from being stranded in another country where my father was essentially my only friend, so if we became estranged from each other for any reason it was like being there alone. But yes, to everything: 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. And any narrative that relies on human arrogance as a plot motivator can't help but seem sadly practical.