Bramble gall wasp

The Bramble stem gall is characterised by a longitudinal hard swelling of the stem, with a length from 2 to 15 cms.
The photo shows a gall prior to the emergence of the adult gall wasps but because old galls can remain on the stem for several years, one is more likely to come across old galls riddled with the exit holes, similar to wood worm, of earlier years emergent adults.
A large gall could contain as many as 200 grub like larvae of the small black gall wasp Diastrophus rubi.