Most caterpillars have four pairs of feet in their central section but geometer moth caterpillars only have two. This means that they are unable to move like the other caterpillars. They use the front pair of feet to hold on to a support, and then they pull the rest of their body up close. Next, they use the pairs of feet in the back part of their body to hold on, and push the front part forward. This means they are often in a position which looks like the Greek letter Omega, as can be seen in the photo. 