I've thought about it a couple of times, but from my childhood experience, most ant bites can hurt. Especially carpenter ants!

When I was little I'd always be watching ants, but I'd always make sure to not stray too close to a carpenter ant nest. Not only are those ants really big, their bites hurt a lot! Once, I went too close to a nest of carpenter ants [some winged female ants were there, too], angered them and owch! They went after me faster than you would think they could, and once they bit me, they didn't let go. I had to have my brother pry them off! Ugh! Makes me shudder when I remember it.

Despite the threat of the ants biting the frog, this would be an interesting idea, but their exoskeletons are tough and I doubt they're high in nutritional value. If you're thinking about food from the garden, go for earthworms or nightcrawlers [big earthworms, basically]. My hoppers love them