Unknown Gall/Egg (Oak leaf)

Unknown Gall/Egg (Oak leaf)

Observation - Unknown Gall/Egg (Oak leaf). Description: Small spherical gall(or egg ?)on underside of oak leaf. Several found ,all on main rib of leaf Only one per leaf

Small spherical gall(or egg ?)on underside of oak leaf. Several found ,all on main rib of leaf
Only one per leaf