An interesting little larvae--hard to see at first on the needles of the pine--but they rear up if threatened, sometimes in unison, creating a rather pleasant ripple effect over the tree.
Apparently, and this accords with my observations of them, there is just one generation of this sawfly in a season, so whatever havoc they wreak now will be the end of it until next year.
They can be removed, vanquished, with soapy water, and there are so many this year that I may take some out.
I have mixed feelings about destroying larvae, caterpillars, etc. They are another way nature turns plants into meat, in this case for birds to feed to their nestlings, so I usually leave them be unless they're going to actually defoliate a tree or shrub entirely, or harm one that is already weakened. These particular critters don't seem to be attracting much attention from birds anyway.
Today's the day that Circus of the Spineless is published--this month's edition is hosted by Bev at Burning Silo--a compendium of invertebrate mystery, tales, and beautiful images. Be sure to drop over and sample the best of recent invertebrate posts from around the blogosphere (and around the world).