Caterpillars of some kind. Blech.

Thanks but what is blech?

:) :) Blech just means yuck...I don't like caterpillars. Sorry...I don't know the type of caterpillar you have. Tent caterpillar maybe??

That is a sawfly larva; I just smash them with my fingers.

I don't think it's a sawfly larva. But, I've been known to be wrong. LOL

I know the creature well as I used to live in Ontario and they did more damage to my roses than any other creature or disease. It is the larva of a large rose sawfly which is non native species infesting Ontario and Quebec, Arge Ochropus, see the image on wikipedia (scroll down for the larva at the bottom which looks like your picture) https://en.wikipedia.org/wiki/Arge_ochropus and here is a blog post by a gardener based in Guelph describing the behavior of the insect https://horticultureforhomegardeners.ca/2021/06/14/rose-sawflies/ -- no photo here but if you've observed it closely you will recognize its behavior from the description. It lays eggs in the soft new growth effectively destroying the flowers as soon as the eggs are laid, though if you are not alert it may take you awhile to notice it. The hatchlings can then defoliate entire canes very rapidly. It is especially fond of spinosissima and any rose bred with it. I cut off any growth I found with the signs of eggs and smashed the larvae when I saw them.

Claire - blech. Our sawfly larvae here are just green and small.

The size is about 5/8 as it says under the picture; the close up is way larger than life. I am familiar with the other types too, all the rose slugs are a pain, but I don't mind any quite as much as this one because of the way it ruins the new buds. I used to get my kids to help me pull them off and smash them.

:) :) Great little helpers!!