or cankerworm or inchworm
Larva of any member of a large, widespread group (mostly in the family Geometridae, with some in the family Noctuidae) of moths .
Loopers move in a characteristic "inching" or "looping" gait by extending the front part of the body and bringing the rear up to meet it. Resembling twigs or leaf stems, they feed on foliage, and can seriously damage or destroy trees.