Yup. But I'm wondering if the one type of behavior might have evolved into the other.
I can't see how eliminating competition among your own would lead to being a predator on a different species. I think that most interesting is if there is some method to where the moth lays its eggs, say to increase the chances of finding a snail (doesn't say if any old snail will do or if only certain kinds are prey). As you know ichneumons lay their eggs directly in(on) their prey. That certainly means that some will be successful. Perhaps the reason is in the lack of insect predators in Hawaii, so they can be slow and allow for many "misses" and still be a successful species.