Many of the looper caterpillars (aka inchworms) of the forest are stick mimics. When disturbed, they hold their body rigid like a small twig. In this way, they blend with their surroundings. The loopers have an abdomen that is flexible and curls to form a loop. The caterpillar grasps the twig with its true legs or its prolegs. By alternating its grip between front and rear, it “inches” along the plant.
Douglas Florian has a poem in his book, Insectlopedia, that describes the movement of the inchworm:
The Inchworm
I inch, I arch, I march along.
I’m just a pinch, a mere inch long.
I stroll and stick on sticks in thickets,
And never pick up speeding tickets.
-Douglas Florian
Looper
Living With Insects Blog 