Berberis Juliana

Also known as Barberry.....I know it has lots of yellow flowers in the springtime. These are replaced with bluish black berries in the fall. They have very sharp thorns which makes them good shrubs to plant around your house foundation to deter burglars.
They like sun or partial shade and are very hardy. I think the leaves turn reddish in the fall.
I have read that the sawfly larva can strip an entire bush in the space of a week but I don't know which species it targets....maybe all of them. Apparently a defoliated plant will leaf out again and recover completely. Spraying with soapy water will probably help control the situation but you would probably have to keep a regular routine of spraying as you might have to with a rose. I don't know if BTK will work or not.
We don't have the berberis sawfly over here that I know of although we have other types of sawfly. So, that's about all the help I can give you. Someone else on GOY will probably be able to help you more.

Thank you Gilli, you have been most informative regarding the Bereris Juliana.
I googled it last night and the page I went to was all about people who had had their plant attcked by this particular sawfly larva, although the people on there referred to it as caterpillars.