Cynips quercusfolii
These marble like galls measuring up to 25mm in diameter are found beneath the leaves of Pedunculate Oak (Quercus robur) and Sessile Oak (Quercus petraea). Cynips quercusfolii is a tiny black gall wasp, and within the plant gall its larva stage grows. On Pedunculate Oak the gall is smooth where on Sessile Oak it is rough and warty. They start off as yellowish-green, turning pink then red towards autumn. It turns brown just before the leaves fall.
The gall and the wasp larva inside matures on the ground and the adult wasp emerges between late autumn and early spring. Eggs are laid in the dormant oak buds where small purple galls are formed. These will bring forth the sexual generation which emerge in late spring and lay their eggs in the new season’s leaves to start the process over again. Seen summer until autumn. Common and widespread.
Photographs of Cherry Gall Wasp (Cynips quercusfolii), taken June and October 2013, local wood and nature reserve. © Pete Hillman 2013. Camera used Nikon Coolpix P500.
Nature Journeys 
Galls are so interesting and I confess I haven’t paid all that much attention to them. Some of them are quite spectacular, aren’t they?
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Thank you for your comment, Melissa. Yes, I agree, some galls are quite spectacular, and I have had quite a fascination for them. I did not realise there were so many different species until I began to take more notice of them and study them a little.
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I didn’t either, although of course it makes perfect sense.
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Interesting post. I’ve begun to notice galls when I’m out walking in the woods but haven’t done much research on them.
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Thank you, Belinda. I find them quite fascinating, especially as there are so many different species, caused by different things like insects, mites and fungi, even bacteria.
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