On a visit to the river Friday, my most bug-crazy gent found some caterpillars. "Can we take them home? Can we take them home?" he begged, jumping up and down. So I pulled some leaves off the plant, stuck them in a water bottle with two caterpillars, and we brought them home.
After much searching of the bug guides, I came up empty-handed. (Or should it be empty-minded? Nah, let's not go there. I couldn't find out what kind of caterpillars they might be, at any rate.) Here's where my farm-girl background helped. When I was a kid, our 4-H club went on tansy pulls. Tansy ragwort is a noxious poisonous weed, and our job for an entire weekend was to search it out and pull it out of the ground. Our club filled a dump truck with the stuff one weekend. So I knew I'd seen these kinds of caterpillars before, and more importantly, I knew that the plant on which we found them was tansy ragwort. I googled something like "caterpillars eat tansy ragwort" and Voila! Meet the Cinnabar Moth caterpillar.
We thought we'd look at them under the microscope. You can see from the picture how well that went. They're way faster than Painted Lady caterpillars.
So we looked at them the old-fashioned way.