Moths, in general, are kind of strange creatures to imagine larger. Mothra, for example, shouldn't be able to fly. Or walk. Or exist. Insects don't really have 'bones', so a large moth (ie, the size of a medium-size dog) would literally collapse in on itself from weighing too much. So mothdogs would have to be really, really light. I'm not talking "chihuahua" light, I'm talking "it's entire mass would not be able to exceed that of a Little Critter book if it doesn't want to collapse in on itself, and that's only factoring 'being able to exist', not the stress of being able to fly and move around" light, assuming we keep all the 'stuff moths are made out of' the same.
TLDR: Big moth make self-squarsh from exist. Dead.
Edit: I'm a handicap. I did my homework on insects, they do have 'bones'. The structure is just weak as forget due to being small, so a human-sized moth is theoretically not going to collapse from it's own weight.
Poll