In the comments, myrmecologist James Trager notes:
A serious question, though, have you ever seen these soldiers eat? I have not and always wondered how they go about it.
Come to think of it, I don’t have much recollection of seeing any army ants eating.
I have never seen a soldier or a queen army ant actively feeding. But last month I did catch some hungry Eciton hamatum workers taking a snack from a cache of pilfered ant brood:
Army ants live such fast paced lives that surely they must feed regularly. Not all captured prey makes it back to the bivouac; at least some is consumed by the ants in the field.
Is it possible that ants simply pass captured prey around to their nestmates, in lieu of trophallaxis? Do any of the army ant biologists who visit this blog know?