If you ever look closely at the leaves and twigs of an oak tree you are likely to notice numerous odd bumps, lumps, balls that almost appear to be a part of the tree. They are likely to be the galls of cynipid wasps (family Cynipidae), and in a sense, they are part of the tree. A gall is a swelling of plant tissue caused by a parasite completing part of its life cycle in the plant. They come in wide variety of forms, and the gall maker can often be identified by the appearance of the gall itself, and the plant species it's found on, without ever actually seeing gall making organism.
Cynipid wasps are a family of minute wasps that specialize in making galls, many of them using oaks as their hosts. Many of them also have a complex life cycle, which I've summarized below in some scribbly notes and a sketch from a previous post on Bullet Gall Wasps; many other cynipids probably share a similar life cycle. With this post I'd like to focus just on the variety of galls I found on just on oak and some of the artwork they inspired me to produce
The large hole probably indicates that the cynipid inhabiting this gall became a meal for a chickadee or other bird.
This gall differs from the others in the post in that it's not detachable (I keep thinking of that King Missle song).
Thank you for touring the Oak Gallery (please note we're closed on Mondays).