Steve's Nature Blog: Minibeast Monday - Oak Gall Wasps: Spangles and Currants

Heart of Oak are our ships,
Jolly Tars are our men,
We always are ready: Steady, boys, Steady!
We'll fight and we'll conquer again and again.

From Heart of Oak, the official march of the Royal Navy. But who is this stowaway aboard the mighty British oak?

“ 'Tis a lowly Common Spangle Gall Wasp, Cap'n (which just goes to prove that all the nice galls love a sailor).”

“And what, pray, is a gall wasp?”

“ 'Tis an Hymenopteran, Cap'n, of the family Cynipidae. The Common Spangle Gall Wasp going under the scientific name of Neuroterus quercusbaccarum. ”

“I'm none the wiser.”

Common Spangle Gall Wasps are very small wasps that use oaks as part of their reproduction cycle. They use chemicals to induce the tree to form distortions on their leaves and catkins which surround and feed the developing wasp larvae. They form two types of galls: the spangles, which are flat, yellowish discs, on the underside of leaves, which turn red as they age; and the currants (pictured), which start green and then turn pink and finally red.

If we cut the gall in half, it's just possible to see the larva in the right hemisphere. This would have emerged in the summer and laid eggs on the underside of an oak leaf to produce spangles. The spangles fall to the ground in autumn, develop through the winter (if they are not eaten) and emerge as adults in the spring. They then lay their eggs, which produce more currants and so on. Then it gets complicated: There are sexual and asexual generations plus two different types of male and female in the sexual generation. And you thought us humans invented LGBTQI?

And finally, if we extract the larva and put it under the microscope we can see... quite a mess of tangled bits and pieces. Top right is an antenna, attached to the head. The basic body shape is there, like a filled in letter 'e', and presumably the structures top left would have become wings. And if you want to know more about galls and wasps, guess what? I've found a few books on the subject. Just click on the pics for a free preview.