La mascotte des géologues

A croire que j’aime les loosers. Ma mascotte préférée a longtemps été le Coyotte dans sa course effrénée après le Bip Bip. J’ai même longtemps rêvé qu’il l’attrapait enfin, ce qui arriva d'ailleurs!

Mais depuis quelques années je lui préfère Scrat, ce lointain cousin de l’écureuil, avec qui il partage la passion des glands et sans qui les aventures de l’Âge de glace ne seraient pas. Il est vrai qu’il est craquant, dans tous les sens du terme.

Ainsi qu’elle n’a pas été ma surprise en trouvant ceci lors d’une promenade. Heureusement, ce n'est pas le crâne de Scrat, il ne s’agit que d’une galle du chêne.

Mon cher Scrat est donc sain et sauf, et pour longtemps, j’espère. N’est-il pas la mascotte idéale des géologues ?

You will tell me that I like loosers: indeed I love Wile E. Coyote always running after the Road Runner. During decades I dreamt that he finally caught him, which he did actually!

But my favourite cartoon character is now Scrat, the real Ice Age hero. So I have been terrified finding this. Fortunatly it is not Scrat’s skull but an oak gall.

My dear Scrat is still alive somewhere. Isn’t it the best mascotte for geologists?

Wasp in jail

Long time ago, I used to accompany my father in the woods. He worked for the French State Forests Department. He taught me all he knew about trees, birds, stars… He stressed the importance of biodiversity and sustainable development. 

I enjoyed asking him the name of every plants and animals on our path. One day I found a small ball on an oak leaf. He explained that this was due to a parasite but was not putting the life of the tree in danger. However I was impressed by the name he put on this: oak gall. 

Galls or cecidia are a kind of swelling growth on the external tissues of plants or animals. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors. They can be caused by various parasites, from fungi and bacteria, to insects and mites. 

Plant galls are often highly organized structures and because of this the cause of the gall can often be determined without the actual agent being identified. On the picture above, the parasite is the gall wasp, also called gallflie (Cynipidae): Cynips quercusfolii. 

Many parts of the tree can develop a gall of very diverse shapes depending on the parasite species and the season. Here on a small branch the parasite is Andricus kollari:

Inside the gall, the larva will be protected and find food during its development. But the gall is also a form of protection for the tree as it insulates the parasite.

If opened, the larva is to be found in the middle of the gall:

Some Cynipidae have two generations every year and two different galls like Neuroterus quercusbaccarum on white oak or Plagiotrochus quercusilicis on Kermes oak. 

Other trees can have galls, namely beech, lime tree, elm, dog-rose and maple, like this one, largely infected:

More trees of the Sant valley