Found new residents in my grey willow this evening. 

There are three groups of this size that I can see.

They are eating the leaves down to the centre vein! Not that I care about the willow, in fact I’m trying to kill it by girdling it (I want to keep the framework for other climbers). I don’t see them in any of my other plants, either.

Any ideas? Are they bad, good, or chaotic neutral?