I started getting interested in galls last autumn from sketching them in my nature diary. I didn’t really realise they were all incubation chambers for gall wasp larvae, but of course when I read more I got fascinated. I picked the Robins Pincushion shown here and kept it over the winter, just to see if anything popped out and said hello. Hey presto, last week I came back to the computer to find a beautiful brown little gall wasp sitting on my keyboard! The gall went into a large jar to be sure, and within a week I had two each of two kinds of wasps.
This was another new bit of knowledge – some galls are incredibly complex societies, with co-habitants, parasites and parasites of parasites such as other gall wasps and ichneumons laying their own eggs into the larvae already inside the gall. I think what I have here are Diplolepis rosae (the originator of the gall, although from images it doesn’t look quite the right colouring), and Periclistus brandtii, which lives alongside Diplolepis in the gall. But I might be totally wrong in these identifications!
CORRECTION 10.3.14: Yep, very wrong on the identification of the brown gall wasp. It’s almost certainly Andricus quercuscalicis – from the Knopper Galls I’d sketched and forgotten I’d left on the windowsill. Because they’d fallen off the tree and had a hole in the base, I assumed the wasps had already left – but despite falling in autumn, the wasps don’t leave the gall until spring.