What's That Bug? does not endorse extermination

Subject: green caterpillar
Location: NE corner of WA state.
June 27, 2017 1:53 pm
I’d like to identify the caterpiller (and it resulting moth or butterfly) in the attached photos. It seems to act like a tent caterpiller but spins a strand and drops down to earth. Most strands get wrapped around each other forming a much larger strand (1/4″ dia) that reaches the ground. This site was on a forest road in NE Washington.
Thanks.
Signature: John McMillan

Caterpillar Swarm

Dear John,
Since it is green and appears to be hairless, this is most definitely NOT a Tent Caterpillar.  Our web searching for caterpillars exhibiting this behavior in Washington has not produced anything significant, however we did find this interesting article Daily Mail concerning millions of green caterpillars on a single tree.  The site states:  “Stuart Edmunds, from Shropshire Wildlife Trust, said he believed the moths could be the larvae of the aptly named ash moth: ‘It is incredibly rare, when there is a limited supply of trees like there is in this area the ash moth mothers could have decided to lay their eggs all in one place. Usually the caterpillars would be distributed over many more trees and with this many on a few trees there is a danger it could weaken the trees'”  Was the phenomena you observed limited to a single tree?  We feel certain this is a moth caterpillar.  Perhaps one of our readers will be able to help us solve this mystery.

Caterpillar Swarm

Thanks, Daniel.
The site in the photos was all in one tree (which looked rather dry and somewhat bare of leaves).
However, we did see smaller versions of this in two other trees along that same patch of forest. We did not identify the trees the ash moth caterpillers were hanging from.
Maybe others will give us more firm data to add to yours.
Cheers.

Caterpillar Swarm

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What's That Bug? does not endorse extermination
Location: Washington

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