Well many thanks David and Lar you have solved this mystery I have always
wondered about. I really didn't think it was the praying mantis as someone
told me but I could tell it was something inside eating it's way out.
Elaine
"David E. Ross" wrote in message
.. .
Christine D wrote:
Hi everyone,
I'm a new member, and this is my first post, so excuse me if I break any
"rules".

My husband was out in the front yard earlier today and came in to tell me
that something was growing on one of our two Oak trees. They don't look
*ANYTHING* like acorns, and I don't believe the trees are old enough to
grow acorns anyway.

As far as I can tell, the trees are probably somewhere between 10-15
years old...I doubt they are any older... They were transplanted from the
forest about between 5-8 years ago by our home's original owner. I'm not
exactly sure of the time frame, but we've been here 4 years, so I'm going
from there...

Anyhow, if someone could take a look at the picture I've uploaded to my
photobucket site and see if they look familiar to you, and if so, what
are they??? They seem to be actually growing on the tree, and look, as my
husband so elegantly put it, like "little green alien eggs".

Here's the link
http://i10.photobucket.com/albums/a1...7/IMG_3362.jpg

Christine

These are galls, sometimes called "oak apples".

They are caused when an insect lays an egg inside the fresh, young tissues
of the tree. The larva that hatches causes an irritation that causes the
tissues to swell. The larva then eats out some (not always all) of the
excess tissues.

When the larva matures and forms an adult insect, it bores its way out of
the gall. The galls you show in the image will eventually turn black and
fall from the tree. They will be very light in weight with a corky
internal texture.

These galls are generally quite harmless to the tree, although cleaning
them up from driveways and lawns can be a bother. Other galls (but not
these spherical ones) can be symptoms of disease, which can cause serious
damage to a plant.

During colonial times, these galls were gathered and boiled to extract
tannic acid for making ink and dyes and for tanning leather.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening pages at http://www.rossde.com/garden/