A reader contacted us about a possible caterpillar that she found in her home. She was unsure if it was a worm or a caterpillar and after we looked at the photo, it is definitely a caterpillar. This creature has some very distinct features and indeed, it is a caterpillar. In fact, it is one of the most well-known caterpillars in the East Coast. It is the Eastern Tiger Swallowtail.