Jumping Oak Gall

A friend found this jumping oak gall on a walkway in the woods here in north central PA.

Jumping oak gall

The jumping oak gall rolls and jumps around - rather fascinating to watch.  The movements are cause by the larva of a cynipid wasp. 
   The jumping oak gall wasp lays its eggs on oak leaves. This causes the galls to form as a shelter and larder for the wasp's larvae. The galls eventually detach and fall to the ground where the larvae can bounce around a bit. Perhaps this enables them to move to an amenable location for pupation.

 I placed my finger in the picture to give you an idea of the size of this little egg-shaped gall.

 One second the gall is just sitting there like any other gall...

 the next second it's flying through the air like a tiny ball.  

    I wonder what it feels like when that gall launching larva lands?  I can imagine it would be similar to the jouncing we used to get when we rolled down the barn hill in a 55-gallon drum... down the hill, across some bumps in the yard, and into the garden fence...thud !

Better yet, imagine crawling into a barrel and launching into the air just by flopping around.
It must take quite a lurch to launch the larva.