Found two yesterday, and just found another one on a different bush today.
The bug is quite big and conspicuous- about 5mm or so long. It has wings.
The head and upper body are black, the lower body is bright orange and soft;
if I squash one, it appears to be orange inside(!) like a sac of soft orange
stuff.

They appear to travel down the stem leaving a black stripe- either cutting a
stripe or laying eggs in a line inside(?), can't easily tell.

Any idea what they are, and if so, are they harmful? I've never seen one
before, but then I've never been a rose gardener before, kind of thing. Any
ID gratefully appreciated.


Ian