Most wildflowers have long faded and due to the continuing drought in our area (Northern California) fungi are scarce while the birds are unpredictable and scattered. Thus while wandering about I find myself focusing on usually overlooked subjects.
Oaks support more gall-inducing organisms than any other group of plants. Since oaks are plentiful, a search for oak galls always results in fascinating discoveries.
Cynipid wasps cause some of the most interesting, odd-shaped and brightly colored galls. Cynipid wasp galls are also species specific and have characteristic colors, shapes and plant locations. Thus the cynipid wasp galls can be identified without ever seeing the tiny wasp itself.
Cynipid wasps have complex life cycles which, in most cynipid wasp species, are poorly understood. Some cynipid wasps have no males and reproduce by parthenogenesis, others exhibit an alternation of generations (heterogeny) while others reproduce sexually with males and females. Some cynipid wasps induce galls while others are inquilines (gall parasites). Much remains to be learned about cynipid wasps.
The ball-tipped gall wasp (Xanthoteras teres) induces a ball-shaped gall on the top of a narrow stalk. These pubescent (finely hairy) galls are one-chambered (monothalamous) and are located on the underside of the leaves of Oregon white oaks (Quercus garryana) and leather oaks. Several are attached to each leaf along a lateral vein. Light green, yellow or rosy, the ball-tipped galls turn brown or dark beige with age. They can be easily detatched.
Little is known about the life cycle of this wasp species.
These ball-tipped galls were growing on the underside of Oregon white oaks near Crystal Lake Fish Hatchery (Shasta County CA).