This was in one of the episodes od Planet Earth with David Attenborough: grizzly bears feeding on moths. Actually, pigging out. They took the trouble to move rocks of considerable size to get at the hiding moths. What was so good about the moth? Fat. Unfortunalty I could not find this bit on YouTube, but here is some info on the phenomenon.
Which makes me think that indeed fat moths and caterpillars could have been a staple in some necks of the wood, along with molluscs. Why bother hunting lean meat when you can just gather the fat a la Mopane! And the fat would be mostly unsaturated (keeps the insect from freezing) with plenty of omega-3. No need for cod liver either.
If environmental issues were to prevent everybody from eating animal protein, farming caterpillars could be the answer. Not necessarily more disgusting than what many people consider food these days. Of course, the caterpillars should not be fed soy - that would be gross.