They may not move very quickly, but it's not because the average caterpillar lacks muscle. Caterpillars have about 4,000 muscles in their tubular bodies, including about 250 in the head segment alone. Compare that to the 629 muscles contained in the human body!
Caterpillars are insatiable eaters, and they move from meal to meal through the contraction of their muscular system. The rear section acts as the engine that powers the body along in a push-pull motion, with the caterpillar's body elongating in between as it makes steady headway.
The little inchworm is a classic caterpillar with a distinctive gait. Also known as a looper, this worm-like creature appears to measure the Earth inch by inch as it moves from one point to the next. The inchworm clasps and reaches in a rhythmic fashion without the help of any appendages in the middle portion of its body.
Other facts about caterpillars: