Even if they are moths, it would still be interesting for the kids to see it. Ask why is it where it is; what do the caterpillars gain from feeding together; are there stripped areas? does it look like the tent may have overwintered? What happens if someone (very gently) touches the nest? What do the caterpillars do? Why? There are some types of butterflies that create nests--mourning cloaks, for example.

My opinion is the cats just did not like the leaves/needles offered to them. Maybe the needles were fir or spruce and not pine. As for the leaves, it could be a regional difference as to why the caterpillars refused the food. I have a lot of imperials this year so I'm trying things I've not tried before. I went out earlier tonight and looked at the imperials I put on hickory and chokecherry. No frass and dead caterpillars. Both are supposedly imperial hostplants but did not work for me. Their siblings are doing fine on sweetgum, eastern white pine, and Norway maple, all hostplants I've used in the past. I had more hatch today so I put some on walnut to see if it works for me. Very sorry to read about your troubles with imperials. The first one I found broke my heart when it refused to eat anything but the pine I found it on. On the first night I had it, it ate every needle I had collected for it. Begged my mom to take us back to get more from the tree but she said I could get other food for it when we got home (were staying about 2.5 hours from home). When we got home, I gave it every type of needle I could find (plus various leaves) but it chose to starve instead of switch. :(

Tent caterpillars for sure, and they can sure strip a tree when their numbers are large like that. Though they do have sprays that will address them, cutting them out and disposing of them is better. Some birds like Cuckoos love hairy caterpillars, so poisoning them can have detrimental affects on birds.

Hypercompe scribonia? "The caterpillar of the Giant Leopard Moth is black and covered in spiky hairs. This hairy type of caterpillar is called a 'woollybear'. It has red rings around it that are most visible when it coils up. It eats the leaves off shrubs, trees and other woody-stemmed plants."