Inchworms are the larvae of a large group of insects called the geometer moths, which are found in temperate climates throughout North America. Their main habitat is the same as their food source: the foliage of woody shrubs and trees.
Inchworm infestations are capable of defoliating entire tracts of trees. Some inchworms are highly specialized to feed upon the leaves of only a handful of species, while others are generalists. For example, the elm spanworm feeds upon elm, while the linden looper consumes linden tree leaves. The spring and fall cankerworms, meanwhile, can be found on ash, oak, beech, apple, hickory, maple and elm trees.