Well, it definitely works for moths and butterflies.
I’ve never had much luck pinning beetles, but It could potentially work for them. And I’ve never heard of pinning caterpillars, so I’m not sure what you could do for them.
There’s a way to sort-of pin caterpillars. Basically, you have to gut them, inflate them, and bake them for a little bit. I’ve never done it myself—but I’ve seen specimens that have undergone the process in a museum. It’s weird and I imagine difficult to do.
Otherwise, you preserve them in alcohol. If you boil them quickly beforehand I hear they keep their colors better for future identification and stuff.
Thanks for clearing that up! I’d feel too guilty preserving caterpillars, I think. I’d rather see them as adults first!