Looper caterpillar. Coloured scanning electron micrograph (SEM) of a caterpillar from a looper moth or Geometroidea family. This is one of the largest moths family. Most of the Caterpillars in this family Geometridae have only one or two pair of prolegs (instead of four pairs). The anal prolegs are well developed. The caterpillars move by curving their bodies into loops. This is why they are commonly called Loopers. They are also known as Inch Worms because they apparently measuring off one inch at a time as they move. Some of them are called Twig Caterpillars because their resting posture camouflages as a twig or stick. Magnification: x50 when printed 10cm wide