Spanworm on Ceanothus

Subject: What the heck is this?
Location: Bay Area, California
February 25, 2015 4:11 pm
Can you please help me identify the creature I found today fervently attached to my ceanothus? It’s the ivory-colored stick-like thing roughly in the middle of the picture.
Thank you!
Signature: CdeP2007


Dear CdeP2007,
This is a Spanworm or Inchworm, the caterpillar of a moth in the family Geometridae.  Caterpillars in this family are often hard to distinguish from sticks, especially when they grasp a branch with their terminal prolegs, extending the body out away from the branch at an angle, much as your image illustrates.  It may be the caterpillar of a Sulfur Moth,
Hesperumia sulphuraria, which is pictured on the Moths of Orange County website.

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