Bean weevils are very easy to culture and my Bombina orientalis love them. They are tiny so they can eat quite a few in a sitting, but they are beetles and thus high in chitin, so they shouldn't be used as a staple. You can culture meal worms, but again they are a larva of a beetle. Lastly, there are various roaches that can be cultured, but I have never done this so I cannot advise you on them.