Wow, that must be one honkin' big sawfly! We used to get larch sawflies on our cascading tamarack but they were teeny.
There were three larvae though I only could find one this morning when I went out to get pics of the plant they were on. It's not a flowering plant so it's not in my book and I have no idea what it is, but maybe you can ID it:
It's pretty chewed up--lots of the leaves are missing. It looks like some sort of willow, maybe? But I don't know for sure...
So if these are elm sawflies, what do they rely on now that the elms are gone?
Thanks for the help, bendy!