wasp galls on fallen
oak leaves floating on duckweed,
I am always amazed at the endless variety of creatures that inhabit our planet. Insects outnumber us larger creatures many times over, yet most of us know very little about their lives. With the falling of leaves from our oak trees, I've been noticing more different kinds of oak galls, most of them caused by wasps or midges. There are over 700 different kinds of oak galls, which may be found on every part of the tree, from leaves to twigs, stems to branches, even on the roots. They come in an astonishing range of sizes, shapes, colors and textures, from apples to Hershey kisses, bullets to brains, sea urchins to oysters, hedgehogs to woolly bears.
Some species of wasps have a complex life cycle. Alternating generations look different and produce different galls. In the spring, female wasps emerge from woody galls on twigs and lay their eggs on the underside midribs of leaves. When the eggs hatch, the larvae cause galls to form and they live inside until they pupate and emerge as adult wasps. The second generation deposits eggs in oak twigs but the woody galls will not appear until the next spring.
All of our oak trees are covered with gouty oak galls that look like blistered balls wrapped around the twigs. These unsightly growths remain on the trees for years, long after the wasp has emerged. Fortunately, none of the galls really damage the tree.
One rather interesting type of gall is the jumping bullet gall, which looks like little brown bullets hanging from the underside of oak leaves. A single larva lives inside each gall and when detached and placed on the ground, the gall hops around like a Mexican jumping bean. Great entertainment for children of all ages.