A reader recently sent us a photo of three worms she found. Two of the worms are large, at least relative to the third worm, which is fairly small. The reader notes that one of the worms is “mature with clittelum,” and also notes that it is dark red. This appears to be so, and it seems that at least one of the other worms has a clittum too. (Thus, we are dealing with clitella, the latinate plural form of clitellum, even though people often write “clitellums,” and hence the addition of this word in the title of this article.) The reader asked us to identify the three worms, which she submitted a picture of, and we have a ready and simple answer: all three seem to be earthworms. We think they are earthworms because they look like earthworms, and the fact that at least two have a visible clitellum lends further credence to this suggestion.
What is that bump on earthworms? You know, the bump somewhat near the center of an earthworm that kind of looks like a segment of a thick rubber band? This may not seem like the most exciting question, but more people than you would imagine are curious about the bumps on earthworms. As a consequence, we decided to write about these earthworm bumps, which are called clitella. (“Clitellum” is the singular form, so plenty of people mistakenly think the plural form is “clitellums.”) What is an earthworm clitellum, and what does the clitellum do?