inchworm

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inchworm,

name for the larvae of moths of the family Geometridae, a large, cosmopolitan group with over 1,200 species indigenous to North America. Also called measuring worms, spanworms, and loopers, inchworms lack appendages in the middle portion of their body, causing them to have a characteristic looping gait. They have three pairs of true legs at the front end, like other caterpillarscaterpillar
, common name for the larva of a moth or butterfly. Caterpillars have distinct heads and are segmented and wormlike. They have three pairs of short, jointed legs (retained in the adult) on the thorax; in addition, they have unjointed, fleshy appendages, called
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, but only two or three pairs of prolegs (larval abdominal appendages), located at the rear end. An inchworm moves by drawing its hind end forward while holding on with the front legs, then advancing its front section while holding on with the prolegs. Inchworms have smooth, hairless bodies, usually about 1 in. (2.5 cm) long. They are green, brown, or black and in many species have irregular projections that cause them to resemble the twigs of the trees they feed on. Many inchworms, when disturbed, stand erect and motionless on the prolegs, increasing the resemblance. Certain destructive inchworms are called cankerwormscankerworm,
name for two destructive inchworms, or larvae of geometrid moths. The spring cankerworm (Paleacrita vernata) and the fall cankerworm (Alsophila pometaria) are named for the seasons at which the adults emerge from underground pupation.
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. Adult geometrid moths range in wingspread from 3/8 in. to 2 in. (9.5–51 mm). Most are gray or brown with fine patterns and are well camouflaged on trees. The cabbage loopercabbage looper,
moth larva, Trichoplusia ni, that feeds by night on the leaves of cabbage and related plants and is a serious agricultural pest. Like the inchworms (of another moth family), cabbage loopers lack walking appendages in the middle of the body and progress by
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 is not an inchworm, but a caterpillar of a different family. Inchworms are classified in the phylum ArthropodaArthropoda
[Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans, insects, centipedes, millipedes, spiders, scorpions, and the extinct trilobites.
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, class Insecta, order Lepidoptera, family Geometridae.