I found these guys beside a walking trail near my home a couple of days ago, and their shade has me puzzled. So dark a grey-brown they appeared black. In fact, since I've had them inside out of the sun, I think their color may have faded some. Possibly a dark form of the tomato hornworm? They seem healthy; i.e. I do not think their color is due to disease or parasites. I'd like to rear them to adulthood, so I've got them in a cage with soil at the bottom, since they will probably burrow to pupate? Can anyone help identify them? Thanks so much.