#365daysofbiking The rise and gall:
September 12th – I’ve been watching the robin’s pincushion gall I found in Darlaston mature as the weeks pass by. I’m interested to see if it shows any sign of being vacated by the insects who grow inside it, and also observe how it decays, to find out what’s under the ‘fur’.
It’s grown redder, and the fur seems to be dying away, with a cavity open on the upper side. I wonder if the wasps have left?
These creations of parasites – unique to wild and dog roses – are absolutely fascinating and I’ll be keeping an eye on this one as autumn draws on.
September 11th – I had promised no more wasp galls. Sorry, just one more I missed.
I’ve been looking at this type of gall for ages and not realised what they are – a small, coffee-bean sized growth, caused by genetic mutation provoked by an injected tiny wasp’s egg. These small, rough galls are tiny compared to the more familiar marble oak galls which are smoother and rounder.
They function in the same way though, as a growth pod and foot source for the wasp larva that hatches within, and when ready, the wasp will eat it’s way out to freedom.
This poor tree at Darlaston had knapper galls, marble galls, common galls and cola nut galls. And plenty of acorns!
August 14th – Sorry, after this I promise no morale oak wasp galls!
This is an artichoke oak wasp gall, created the same way as all the others, this wasp selects acorn buds, which are corrupted into these neat little artichoke shaped growths to house it’s larvae.
These examples spotted on Clayhanger Common.
That’s it now, I think we’ve collected the set…
August 13th – More oak wasp galls, which I’ve gone all out to find this year for no other reason than they fascinate me.
On a small sapling by the canalside track at Hopwas, hundreds of thousands of almost annular, ring-like growths on the leaves, looking maybe like fungus or some odd egg. These are the delightfully named common spangle gall for the flat ones, and silk button galls for the rounder, more sharply defined ones.
These are all created by the same mechanism – a small wasp injects an egg into the leaf, and a chemical coating the egg disrupts the plant DNA to grow the gall, which leaves a light patch on the upper surface of the leaf where nutrients have been leeched away by the larva growing underneath.
I’m not sure why galls like this captivate me so much but they are absolutely fascinating.
August 10th – Oak galls continue to fascinate, and on this tree in Victoria Park, Darlaston, there’s quite a display of knopper galls, the first I’ve seen this year.
Like other oak parasites, the knopper wasp lays eggs in it’s host, secreted in a chemical that corrupts the cellular DNA of the host plant matter causing the gall too grow. In this case, the target is the acorn itself, and on this tree, one can see some acorns blighted by two such galls.
As with others, the egg hatches and ithe wasp larva eats the gall and grows safe in it’s corrupted acorn, before boring it’s way out when mature.
Also on this tree, the more conventional wasp gall – the common ‘oak apple’ of folklore, a spherical gall grown the same way.
These galls don’t harm the host, but do reduce the functional acorn crop. I’d love to know just why the oak is targeted so particularly with the and not so much other trees…