Also you can put them into a container the afternoon before feeding them off and they will eat certain veggies and leafy greens. I've fed them red peppers/green peppers, collar greens, dandelion greens, kale, lettuce, grated carrots , sliced celery and just about anything else you can get cut thin enough so it's easy for them to eat.
EDIT: Collard greens, thinly sliced carrots and peppers seemed to work the best. You wouldn't believe how much of those three a single medium sized worm can eat in a 12 hour period.