Inchworm, Spanworm

Inchworm walking in Schenley Park, 4 Sep 2026 (photo by Kate St. John) 13 September 2026 Earlier this month I saw a caterpillar dangling from a silken thread as he descended from a tree in Schenley Park. Inchworm dangling from a thread out of a tree, Schenley, 4 Sep 2026 (photo by Kate St. John) The wind moved him gently to and fro, far and near to me. When he was about to bang into a runner, I reached out and grabbed the thread and it clung to my sleeve. I deposited him in a paved ditch were I could take his picture. Inchworms, also called spanworms, are the caterpillars of geometer moths (Geometridae), a large family of moths with a global distribution including over 1400 species in North America. Their family name geo+meter means “earth measurer” and refers to the caterpillars who appear to be measuring the earth as they walk. Because this inchworm came out of a tree, trees are probably his host plant. He might be the caterpillar of a maple spanworm moth (Ennomos magnaria), a…