Tough to tell through that container. The spikes lead me to think it is one the Brushfoot butterflies. Maybe buckeyes.

I can't see them either. What leaves were they eating when you found them?

Sherry

I live in Idaho, maybe my location would help? I didn't find them anywhere. My bio teacher gave them to me to keep and take care of but I want to get a better understanding of what exactly I'm taking care of

With that scenario, they are most likely painted lady caterpillars. They just live off the stuff at the bottom of the cup. Only thing you might want to do is separate them into two cups since the relationship could go south when it comes time to pupate.

Raising painted ladies

After looking at these instructions/pictures, I'd say you don't need to separate them.

Butterfly Kit Instructions