taken 11 years ago, near to Bourne, Lincolnshire, England
Lots of galls
Oak trees pay host to a wide variety of infecting insects, many of which are cynipid wasps, which have a strange double reproductive cycle - female-only wasps reproduce by parthenogenesis, and lay eggs of a normal male/female generation who mate and in turn generate the next asexual females.
The two large green galls are probably the Cherry gall caused by the asexual female phase of a gall wasp 'Cynips quercusfolii'. I was taught that you only ever get one per leaf, but that seems to have changed in recent years. There is a Pea gall, but it is smaller and smoother. These will turn red toward Autumn, hence the 'Cherry' name.
The brown scales are Spangle galls, possibly the best known oak leaf gall. These are home to the asexual phase of 'Neuroterus quercusbaccarum'. The spangles fall off in Autumn (oaks notoriously keep their leaves late) and form a valuable food for birds. Those that do survive winter in the leaf litter will emerge, mate, and lay eggs on male catkins that form bright red galls up to 5mm in diameter!
The lilac-coloured galls on the same leaf might be Schenck's gall - the bisexual generation of 'Neuroterus albipes'. The galls of 'Neuroterus quercusbaccarum' and 'Neuroterus albipes' are both highly variable, and this colour is unusual for both.
On the leaf behind the toroidal galls are another common oak infestation, the Silk-Button Spangle Galls caused by the asexual cycle of the gall wasp 'Neuroterus numismalis'.
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