“What is this thin, small, brow/tan, almost greenish inch worm?” writes this reader about the worm-like organism pictured below. “Found it dangling off my cap on a some sort of thread I think, it moves pretty fast. From the US.” Thanks to our reader’s excellent photo and video, but mostly the fact that she names the organism herself, we can confirm that this is indeed an inchworm. Inchworms are any caterpillar of a group of moth species found in North America. They are all characterized by their number and placement of appendages: legs at the front and back, but not in the middle. Due to how the legs are positioned on the body, the inchworm moves as it does in the video: by reaching for something to grab onto with its prolegs, then arching its back while the hind legs catch up.