I found two of these guys in my bushes last weekend, one was roughly 4 inches and the other was roughly 3 inches. My two kids were extremely interested in them and after looking on the internet and determining that they were not dangerous, we captured them. I looked more information up on them and came to the conclusion they were tobacco hornworms, I am not sure if this correct after seeing that my little guys have green horns. I thought they burrowed underground so we added dirt to the tank. The largest one went into the ground the next day (this was roughly 3 or so days ago). I decided to check on him and discovered he is still a caterpillar, I thought he would have gone into a cocoon by now. A startling thing though is the smaller one did the craziest thing. He shrank! No joke, he went from 3 inches long to the size of a normal caterpillar. How is this possibly? Could anyone help me? Also why did the larger one burrow and not shrink?