This weekend, I had the chance to visit the Discovery Museum in Sacramento, CA. While the museum itself was pretty awesome for a small space, I was most intrigued by something I saw outside. The museum is surrounded by trails with some riparian habitat and plenty of oak trees in the area. Typical California woodland. All these oaks had these funny looking “apples” all over them which are really not apples at all. They’re called galls, and are actually quite common if you know where to look. Often, wasps or flies will lay their eggs in plant tissues (leaves or stems of plants) to develop. The immature insect emits chemicals that mimic plant growth hormones thereby creating a protective covering for themselves as they develop. Once they’re mature, they chew their way out of the gall and fly free!
This is a great blog post about the Oak Gall Wasps of California: Left Coast Naturalist: Oak Gall Wasps – the Cynipids.
via Oak Gall Wasps.