Inchworms got their name by seeming to measure the ground
Geometridae means earth-measurer: larvae with only two or three rear proleg pairs hitch forward in loops, so people call them loopers, spanworms, or inchworms. The family holds about twenty-three thousand described species; more than fourteen hundred live in North America alone.
Many inchworms run about twenty-five millimetres long, coloured green, grey, or brown to vanish among twigs. Disturbed, they freeze upright on their prolegs and look even more like sticks; some add humps, filaments, or plant debris. Diets range from lichen and pollen to, in Hawaiian Eupithecia, animal prey. The cabbage looper and soybean looper are not true inchworms but belong to another moth family. Peppered moths of this clan became classic subjects in population genetics, and several other geometrids are notorious crop pests.
Adults tend to have slender bodies and broad wings held flat so the hindwings show, looking almost butterfly-like while remaining night-flying moths with a frenulum linking the wings. Most span about three centimetres, though extremes run from ten to fifty millimetres and a few Dysphania grow larger still. Males often wear feathered antennae; some females, such as winter moths and fall cankerworms, have reduced wings. Paired tympanal organs sit at the abdomen base in flying forms.
In two thousand nineteen, German researchers described Eogeometer vadens, a five-millimetre caterpillar in Baltic amber about forty-four million years old from the Eocene, the earliest evidence for Ennominae tribe Boarmiini. Molecular trees now sketch eight large clades roughly matching traditional subfamilies, though Oenochrominae splits across three branches. Later work places Larentiinae, with about fifty-eight hundred species, as sister to the rest, and a Sterrhinae-plus-Oenochrominae clade as another deep split. The looping gait that named the family still defines how most people meet them.
Source: Geometer moth
