One of our readers sent us an email describing some worms that they had found on their trees. She said that they had always called them Topa worms and the tree a Topa tree.

We received a question a few days ago about small worms that spin a “thread like line from vegetation.” (The worms’ threads are probably found mainly on trees, and hence our title, but they could be on other plants as well.) The reader lives in Arizona, and only sees the thread-spinning worms at night, or at least this is when the worms are believed to be creating their threads. (The reader is ambiguous on this point.) The reader was only preoccupied with identifying the small worms, so we’ll limit ourselves to this matter, only concerned with the question “what are the small worms that spin threads and hang on trees?”

What type of small, green worms hang on silk threads? A reader recently sent us this question after observing some worms “floating” outdoors (and, to be fair, small worms that hang on thin threads of silk often do look like they are floating around). They didn’t mention where they found the worms, but since the reader seems to be describing inchworms (sometimes written as “inch worms”), there is a good chance they were hanging from oak trees. So, what exactly is an inchworm, and why do we think this is the creature our reader found?