Neat (but voracious) caterpillar, Orgyia pseudotsugata

We found this caterpillar on a ground peony in our garden this morning.


It is the larval form of the Douglas Fir Tussock Moth, Orgyia pseudotsugata. They are, like most caterpillars, voracious eaters and can have a devastating effect on Doug fir forests. Spraying, of pesticides or pheromones such as microbial insecticide Bacillus thuringiensis, and insect growth regulators, is often used against tussock moth infestations. Human activities, such as monoculture forest plantations, suppression of forest fires, and elimination of potential predators, have encouraged tussock moth proliferation.


We were able to make a pretty firm identification of the caterpillar thanks to a terrific book, Lepidoptera of the Pacific Northwest: Caterpillars and Adults, by Jeffrey C. Miller and Paul Hammond. [Forest Health Enterprise. H.J. Andrews Publication Number 3739. December 2003. The authors work at Oregon State University in Corvallis.] Each page has a good photo of the caterpillar and adult forms of one species, with descriptions of appearance and ecology, such as what plants they are likely to be found on. Great book! Your tax dollars at work!

You can view or download the book as sections in pdf form. This moth is on page 175 of this pdf section. The book, an oversize paperback, is published by the USDA Forest Service, and was available several years ago (& still may be), free or very cheap, from
Richard C. Reardon
USDA Forest Service
180 Canfield St.
Morgantown WV 26505

Here’s a photo of the cocoon form, woven around dead Doug fir needles. [Photo by William M. Ciesla, Forest Health Management International] Lots more information and photos of Orgyia pseudotsugata here and here.


The Douglas Fir (Pseudotsuga menziesii) is an extremely common forest species in the West, a primary source of lumber, and is the state tree of Oregon. Notice the distinctive cone. [Image from Encarta.]


2 thoughts on “Neat (but voracious) caterpillar, Orgyia pseudotsugata

  1. I have only just seen your image of a caterpillar of Orgyia. May I offer a suggestion that it is not O. pseudotsugata but more likely O. cana (sometimes referred to as the Western tussock moth). Very closely related but found more frequently in lower elevations of California. I would be interested to know where you found your specimen.

    Regards, Paul Schaefer

    • Hi Paul,

      Thanks for your comment so long ago…Health issues in the family have kept me from my blog. Our ID of the caterpillar is done layman-fashion, looking for a photo match and seeing if it would occur here; we have some good books including a forest service guide to butterflies and moths of this particular area, but we could easily be wrong. The area is the Siskiyous, 8 miles from the hamlet of Ruch. The coordinates of Ruch according to Google are 42°14′12″N 123°2′28″W. We are about 20 miles from the California border.

      What do you think about the species ID?

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s