Erannis jacobsoni
Erannis jacobsoni, or Jacobson's spanworm, is a moth of the family Geometridae. The species was first described by Alexander Michailovitsch Djakonov in 1926. It is found in Europe and Asia.
[Image:Erannis jacobsoni infestation.jpg|thumb|left|200px|Infestation]
The larvae feed on Larix species, including L. gmelinii and L. sibirica.