A gall formed on Oregon white oaks (Quercus garryana – see “Oaks in Spring” 03-05-14) by the cynipid wasp Trichoteras tubifaciens is the crystalline tube gall.
A tubular-shaped gall covered in short, crystalline hairs, the crystalline tube gall ranges in color from creamy to yellow with red bristles to completely dark red. This monothalamous (one larval chamber) gall is found on leaf undersides along the midrib. It usually occurs in tight clusters of up to 35 galls. A small opening at the top of the tube leads to the larval chamber. It is suspected that the adult exits the gall through this hole.
Like so many of the cynipid wasps, the life cycle of T. tubifaciens is not well understood. Female crystalline tube gall wasps have been found in the larval chamber in late fall. These females are thought to emerge from the gall during the winter. There is still much to be understood about these tiny gall inducers.
These crystalline tube galls were found along Crystal Lake (Shasta County CA). Note the one leaf with both crystalline tube galls and sunburst galls (See “Sunburst Gall Wasp” 09-12-14).
Not much may be known about these galls and their causative cynipid wasps, but they are fascinating growths.