I have spent a large part of today sorting out my nature table which is now overrun with twigs and bits of leaves, many seed pods, cones and dried leaves. The pods from the milkweeds have burst open and errant fairy seeds waft around the room with every breath of air. It's truly a jumble, but in amongst it all was this small leaf I had picked up one day, with two wasp galls firmly attached to the underneath. It's such a pleasing object. Not quite a exquisite as the potter wasp's beautifully made pot which I still have here, and not as comical as the gouty galls I drew some time ago (both here). But the simple arrangement of two perfect little spheres on this leaf make this wasp a bit of an artist.
Galls and other insect built homes are fascinating but these are particularly creative. They are the designs of the Gall Wasps, Family Cynipidae, who, although wasps, are tiny, often no bigger than a fruit fly. The galls are formed by abnormal growth of the plant cells stimulated by chemical secretions produced by the wasps either feeding or laying eggs. The plant tissue grows up around the eggs to protect the larvae, but why they are such extraordinary shapes and colours is a mystery. I can see that some imitate twigs but something red and spotted is not really very well camouflaged.
There are saucer galls, beaked twig galls, dunce cap galls, red cone galls, and spined Turk's cap galls and everywhere I looked I found more. But this site, BugGuide. net here will give you wonderful identification photos by a variety of photographers. Here are some of the examples.
Spined Turbaned Gall
Beaked Twig Gall
Spiny Leaf Gall
More photos and a informative article from Hawk Conservancy Trust .org here
Robin's Pincushion Gall
There is an excellent and informative poster "Wasp Galls on Californian Oaks" by Ron Russo here . His comment rings true, "the behaviours and structures that have evolved for the successful survival of Gall Wasps are among the most intriguing stories of nature" It's a great poster.. Hmm.. decisions? .. If I just move the Nine Inch Nails poster over a bit, there will be room for the Oak Galls.. :).
But they are fabulous aren't they? I realise now I have a couple more which I thought were tiny fungi growing on a twig. I may draw those tomorrow.