I personally would never feed chams crawlers or reds. They live and the ground which in itself is very unlike anything a cham would naturally eat. Worst of all is that they're prone to have parasites. I wouldn't feed them to your cham if I were you. Stick to the regular stuff crickets, dubia, butter worms, silks, and super worms. there's a bunch of others but that's what I usually use.
Hope it helps
Scott
If they are farmed it is probably much safer- there are out of ground worm farming containers of all sorts on the market.
I used to feed my veileds earthworms sometimes. Most chameleons don't like them, veileds will often take them. They are pretty nutritious, but I suppose unnatural like the other poster pointed out.