It is quite a regular thing for me to see something that makes me marvel at how amazing nature is. Every now and again though something really does make me catch my breath. It was one of those moments a couple of weeks ago.
Now I think galls are pretty amazing – those strange lumps, bumps and balls that you see on trees. The idea that an insect can lay its egg in a plant and then change the chemistry of the plant to get it grow a protective case around the egg is mind blowing.
One type of gall that you can see a lot of at the moment on the underside of Oak leafs are Silk Button Galls. These house the eggs of a gall wasp called Neuroterus numismalis. These eggs develop and continue to grow even after the leaf has dropped off the tree.
This is incredible enough but when I was drawn over to see what two other volunteers were looking at, I was lucky enough to see another wasp, Torymus nitens. Now this beautiful tiny green wasp lays its eggs inside the gall so that it can feed on the unfortunate grub inside. Apparently the Torymus nitens wasp can detect whether any other Torymus nitens has already laid its egg and, if the coast is clear, uses its large ovipositor – a special organ that looks like a sting – to get inside the gall and lay its egg.
(Photo by Andy Purcell, 2017)
So Neuroterus numismalis parasitizes the oak tree and then Torrymus nitens parastizes the Neuroterus numismalis. The natural world really can blow your mind! You just need to take the time to look; and if you see people peering closely at something – go and ask them what they have seen.