A big family of heterocerous lepidopterous insects or moths: The Geometridae includes the geometrid, geometrid moth whose larvae are called "measuring worms".
The name Geometridae is derived from Latin geometra which came from Greek, "geometer, earth-measurer".

This refers to the process of locomotion of the larvae or caterpillars, which don't have the prolegs of other Lepidopteran caterpillars in the middle portion of the body, with only two or three pairs at each end.

Equipped with external body parts that project from the body at both ends of the body, a caterpillar will grip with its front legs and draw up the hind end, then it will clasp with the hind end (prolegs or the fleshy, stumpy legs on the hind region of caterpillars) and reach out for a new front attachment all of which give the impression that it is measuring its journey.

The caterpillars are accordingly called "loopers, spanworms", or "inchworms" because of their characteristic looping movements.