They are Hyles lineata right? They can be safe to feed off depending on what they feed on. As long as they haven't been eating a toxic plant, they should be okay to feed off in the worm/moth stage. There are some artificial diets that have been created for this specific species, but since it is a generalist, I would think that you could raise them on hornworm chow (though I am not positive, but I think you have a good chance of being able to do so.) I have fed some of these off before. Where are you located? The host plants might be different depending on where you are. Around here, they will eat the leaves from willow, apple, tomato plants, evening primrose, grape and some others. If you dont want to try/can't get hornworm food, I would try grape leaves if you can. They are good to add to a gutload, so the worms will already be gutloaded for you!