These sawflies were found on White False Helebore, Veratrum californicum v. caudatum. There were many of these insects on the plants and apparently eating them, based on many holes in the leaves, and mating. On May 31, 2014, I found and photographed larvae (100s) on the same plants completely defoliating this extremely toxic Helebore - see photo # 1055652. I'm wondering if these are Tenthredinidae? To me it is fascinating that these tiny insects can safely ingest Helebore and perhaps use it for defense.