"Ian B" wrote...
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.

Sounds like the Rose Slugworm or Rose Slug-sawfly. the lavae are
yellow-green and caterpillar shaped and will eat the top of the leaf. This
Sawfly does not roll the leaf or, usually, eat the underside of the leaf
unlike a lot of other Sawflys.
Confirm it by checking the photos on...
http://bluewisteria.co.uk/pest/pest_...e+sawfly+larve
--
Regards
Bob Hobden
W.of London. UK