measuringworm

[mezh-er-ing-wurm] /ˈmɛʒ ər ɪŋˌwɜrm/
noun
1.
the larva of any geometrid moth, which progresses by bringing the rear end of the body forward and then advancing the front end.
Also, measuring worm.
Also called inchworm, looper, spanworm.
Origin
1835-45, Americanism; measuring + worm
British Dictionary definitions for measuring worm

measuring worm

noun
1.
the larva of a geometrid moth: it has legs on its front and rear segments only and moves in a series of loops Also called looper, inchworm