Robin's pincushion

I have seen much more Robin's pincushion recently than in previous years but until now nothing like this.  We came across this rose bush on a coastal walk just north of Dunstanburgh castle and it is smothered in galls.

They are caused by the tiny bedeguar gall wasp Diplolepsis rosae.  It lays its eggs in leaf buds on wild rose, causing the development of a gall in which the larvae feed, grow and shelter, emerging next spring.

Over 99% of the larvae are female, being produced by parthenogenesis.  The females are infected with a bacterium, Wolbachia, meaning they can only produce diploid eggs, hence female offspring.  Female wasps treated experimentally with an antibiotic can produce haploid eggs and male offspring!

The Robin in the name was Robin Goodfellow, a woodland sprite in folklore.  He was also known as Puck or Hobgoblin.