measuringworm

or meas·ur·ing worm

[ mezh-er-ing-wurm ]
/ ˈmɛʒ ər ɪŋˌwɜrm /

noun

the larva of any geometrid moth, which progresses by bringing the rear end of the body forward and then advancing the front end.
Also called inchworm, looper, spanworm.

Origin of measuringworm

An Americanism dating back to 1835–45; measuring + worm