A reader recently sent us an excellent photograph of what appears to be a Tiger Swallowtail caterpillar. The reader was only wondering what kind of “worm” she found, so we’ve already answered her: she didn’t find a worm, but rather a caterpillar, and we are pretty sure this caterpillar is a Tiger Swallowtail caterpillar. However, we can’t just assert this without giving any explanation, so we’ll quickly supply one and then come to a speedy conclusion.