The California Gall Fly is actually a kind of gall wasp, and it not a fly at all.
This photo of a gall wasp is by Dr. Ed Ross of the California Academy of Sciences.
This is a gall from a vally oak at the Ranch, collected July 4, 2010.
Note the structure of the gall: a hard shell, a vascular stem-like structure leading from the
point of attachment at the left to the center where the larvae live. There is a somewhat uniform structure
of the rest of the gall.
This is a view of the gall wasp larvae, through a microscope.
Note that they have created a chamber with a wall, right at the end of the linear structure that leads from the branch to the insects.
The linear structure is almost like a straw, bringing sap from the tree to the larvae.
This is a higher power view. On the larva to the right, the head end is to the right.
This is the structure of most of the gall. It is composed of vessel-like structures that are filled with sap
when the gall is growing. There are air spaces between the vessel-like structures.
At maturity, the sap is gone and they are empty air chambers.
This is a very high magnification view of an dry vessel.
Rancho Hondo Insects |