Marble Galls

Leaves, Oaks and Galls …….

At this time of year leaves are a problem at the museum, they blow in all the building, block gutters and drain gullies which have to be cleared. Below is an article about this time of year and oak trees by a good friend of the museum Rex Hancy.

Huby Fairhead

Marble Galls ……..

As leaves fall from the oaks, so the hard, round spheres known as marble galls become more conspicuous. During late summer they were still green and difficult to find. By now colour has gone and they appear dull and dead.

Appearances can be deceptive. In the heart of each there should be a single gall-wasp grub ready to pupate and eventually emerge as a tiny adult to lay eggs on spring catkins and leaves. The galls then produced are nothing like the marble galls we see now but that is another story.

In nature, little is simple. Though now it looks like an impregnable fortress, when the marble gall was still tender, a parasitic wasp may have laid an egg next to or actually in the body of the proper occupant. Other, almost minute, wasps may have deposited eggs in the outer fringes so their offspring hatch in an abundance of free food.

Old, last years marble galls should have a conspicuous hole from which the true occupant emerged. There may be many other smaller holes showing where parasites and lodgers left the gall and entered the wider world as adults.

If you find such a gall, try placing a pin every such hole and count the total. You may have a surprise.