We recently heard from a reader who asked, “Do inchworms have backs?”

Despite their name, inchworms are actually caterpillars not worms. Inchworms survive on fruit and leaves, and eventually will turn into geometer moths.

While inchworms do technically have backs, they do not have the same bones in their backs that humans or some other animals do.

Where humans have an endoskeleton, or an internal skeleton, inchworms have an exoskeleton, or an external skeleton. This outer layer protects and supports the inchworm, and can even be considered a shell in some ways. In addition to the exoskeleton, the inchworm also has a hydrostatic skeleton. A hydrostatic skeleton is found lots of soft-bodied animals and it consists of a fluid-filled cavity that is surrounded by muscles. These muscles can expand and compress in different ways to produce a wide variety of movements.

To sum up, our reader asked about inchworm anatomy, and we shared some of our knowledge about these creatures!