Erannis jacobsoni, Jacobson's spanworm, is a moth of the Geometridae family. It is found in Europe (Russia: eastern Siberia, the Russian Far East and western Siberia) and Asia (China: Nei Menggu, Japan: Hokkaido, Honshu and Shikoku, Kazakhstan and Mongolia). The larvae feed on Larix species, including Larix gmelinii and Larix sibirica.