When you see wild roses, check for these very distinctive galls.  They are not on every bush by any means, but are quite easy to spot at a distance because they are large and distinctive.  Old galls remain on the bushes, but may lose their 'hair'.

The wasp itself will be very difficult to see, and even more difficult to identify, but the gall is unique, so makes our job a lot easier!  Galls can be kept in a muslin-covered container to see what emerges - not just the gall-causer, but a suite of parasitoids (insects which develop as parasites on the larvae of of the gall-causer) as well.

Keep it in mind in autumn and winter as the leaves drop from the roses and make the galls easier to spot.

Photo © Björn Appel at Wikimedia Commons.