Subject: Unknown Bug
Location: California Bay
November 20, 2012 11:30 pm
Hello there. There are these strange looking bugs that have been seen near where I live (Pacifica and San Bruno California) and I have no idea what they are. Can anyone identify them? I’ve never seen anything like this before!
I’ve seen more than one now, they are very hairy and squishy. They have at least 4 or 6 legs (near their head) and they are always attached to a hairy sack with a hallow black exoskeleton inside and next to what looks like an egg sack. They have wing-like appendages that are small and hairy near their heads.
Signature: Alexsis Johansen

Flightless Female Western Tussock Moth with Egg Mass

Dear Alexsis,
Your description is perfect and it could not be more accurate.  This is a flightless female Western Tussock Moth,
Orgyia vetusta, and we identified it on the Moth Photographers Group Flightless Females page, but there is even more information on the Moth Photographers Group Tussock Moth Parasitoids page that documents the life history as well as a significant parasitoid predator, a species of Tachinid Fly.  According to Joyce Gross of the University of Berkeley:  “Adult females are wingless. When they emerge from the cocoon (eclosure) they remain upon it and release a pheromone, a sex-attractant that brings males to her. The large antenna of the male is very sensitive to the species-specific pheromone and any males downwind of the female will quickly follow the scent to her location.”  There is also a very nice photo on BugGuide of a newly emerged female.  You can see photos of the caterpillars of the Western Tussock Moth in our archives.

Update from November 22
Now that I have viewed the website I have realized that I have been seeing those western tussock moth caterpillars my whole life and I never would have guessed they would turn into that moth! That is truly amazing. Here is a photo that I took of the caterpillar a few months ago. Thank you so much for your response!

Western Tussock Moth Caterpillar

Hi Alexsis,
More than a week has passes since you submitted the caterpillar photo, but we were away for Thanksgiving, and there is way more mail in our inbox than we can read.  We are updating the posting with your new photo.


Location: California

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