I found 5 of these perched on one of my roses. We must save insects, I thought.
I looked it up and it is a large rose sawfly.
The female, like all sawflies, are in possession of a little saw. With it they make parallel cuts in the fresh shoots of the rose. In the cut a bunch of eggs is deposited. The larvae hatch quite quickly and move in a group to the freshly emerged leaves. The young larvae (yellow with black spots) stay together for quite some time, capable of eating the entire shoot. Older larvae lead a more single life and eat from older leaves as well.
My conclusion Friends is that I have plenty of roses and the world needs insects.
Submitted by Hilary Mayne