Steve's Nature Blog: gall wasp

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.

Paperback £12.65

Hardback and Paperback £12.00

Hardback £19.67 Paperback £16.25

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All the best,

Steve

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Ichnofossils

Okay folks, that’s our challenge for today. Somehow we’ve got to find our way down there and try to descend once more into the valley. But before we go haring off to find the possible route of descent I’ve just noticed a bit of stone that looks somewhat intriguing. As you can see there are dark patches running through it and if you look closely you can see that they are radiating outwards from a common point below the stone. Take a closer look under the hand lens. There are faint tracks showing that the structure is branched and some clusters of dots, some of which are in pairs. Both of these tell a story of burrowing creatures on the sea bed in the geological past and it introduces us to the little known science of ichnology¹. Just as historians can piece together a story from ancient human artefacts, ichnologists study these trace fossils, or ichnofossils as they are technically known, to build up a picture of the creatures that made them. Fascinating forensics if you’re looking for a new hobby and serves to remind us that the landscape we’re walking through has a long and detailed history. We’ll leave it somewhere conspicuous and pick it up on the way back. The descent is going to be tricky enough without carrying bloomin’ great rocks around with us.

Sage galls and wasp, Cynipidae

Here we go then, but on your trip down have a look in the sage bushes on the way and see if you can find some galls. I read something the other day which I want us to check out. This is the Greek Sage, Salvia fruticosa, and some years back I was given some “sage berries” by a neighbour as a local delicacy. At the time I didn’t realise that I was eating insects (and neither, I suspect, did they). Anyhow, back in Israel in 2001 it was discovered that these particular “berries” were galls produced by a new species of Cynipid gall wasp². Now, I’ve noticed over the past couple of weeks that there seem to be two different types of gall: one which is produced from the side of the stem and one which is produced at the tip. The question is: are they produced by the same species of wasp or from two different species? Ah, well done, you’ve found some tip types, with and without exit holes. We’ll have a look at them under the microscope later and meanwhile, we’ll keep our eyes peeled for the other type. Incidentally, eating insects as a method of feeding the world is a bit of a hot topic at the moment. A good idea do you reckon or just another way of destroying the planet’s biodiversity?

Scorpion, Mesobuthus and Scorpius constellation

We’ve reached a thirty foot vertical drop which will restrict our downward progress somewhat. Never mind, we’ll go back a bit and try to get around. However there’s a nice fallen pine here in a state of decay so let’s probe the depths and see who’s about. That’s rather a nice scorpion you’ve found there, somewhat larger than the small wood scorpions we’ve been seeing recently. Now I know that I said “There are only about two dozen or so potentially lethal scorpion species out of the fifteen hundred or so that are known to science and, as far as I know, none of them live on Crete.” – (See The Misty Thripti Mountains ) but I’m not sure that this one has been recorded on Crete before. It’s a Mesobuthus, a genus that contains some very venomous species. I’ll just take that piece of wood from you and put him back. Seeing him in that position reminds me; the constellation Scorpius is very easy to recognize at this time of year. If you look to the south for the red star Antares the shape of the scorpion really does look like the one you just found. Well yes, I quite understand, it probably won’t be the last thing you want to look at before you go to bed tonight.

Galatella cretica

How about looking at some pretty flowers by way of something different? I mentioned these Galatella in passing a couple of weeks ago but they’re really in bloom right now and I love the way that they change colour from a pale green to golden yellow and then a deep magenta. The one colour that they aren’t is white which is strange for a plant who’s name begins with ‘gala’ as this is the Greek for milk. I wonder if it’s a diminutive of Galatea, the sea nymph who was in love with Acis and turned him into a river spirit after the jealous Cyclops, Polyphemus, chucked a boulder at him? Even so Galatea still means ‘she who is milk white’ which doesn’t really fit with the flower colour.

Crag Martins, Ptyonopogne rupestris

We seem to have come full circle and it’s pretty evident that we’re not going to get back down into the valley from this side. Still, we’ll pick up our trace fossil and try from the other side next week. Hang on though, what are those flitting about behind the car? Well I’m blowed – do you remember that patch of mud we drove through just before we parked up? It seems we must have churned it up enough to be useful to a flock of Crag Martins. A few weeks back English twitchers were hammering up and down the motorways to get a glimpse of one of these birds and we’ve got a couple of dozen of them right here. It’s surely too early for breeding but crag martins reuse their nests each year so maybe they’re doing a bit of winter maintenance whilst the materials are available. Could be they even use them as bad weather roosts when the storms hit? As always there are many more questions than answers.

Until next week then – Happy hunting.

1With thanks to Mike Hardman and Dr T via the Natural History Museum, London for identification of the trace fossils as Chondrites, Arenicolites or Diplocraterion and other ichnogenera.

2 New Genus and New Species of Cynipid Gall Inducing Wasp (Hymenoptera: Cynipidae) and New Species of Chalcid Wasps (Hymenoptera: Chalcidoidea) from Israel

See all the pictures including insets in detail on Flickr

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LINKS:

Naturalists (the facebook page that accompanies this blog)

Greek Butterflies and Moths

Aquaworld Aquarium

Visit Greece (National Government Tourist Office)