termites ?

Hi, 

We have an eichler in Northern California and noticed warping on our walls.  I thought it was water damage from the shower in the room but the wall seems to be of plywood.  Peeling some the affected areas back, there seems to be dust and small cavities.  No bugs though.

I am going to try attaching a link with a photo in the hopes if someone who is familiar with this might be able to help.

thanks,

Ed