This may not look much like a residence, but it is for a tiny little wasp in the Cynipidae family, probably Disholcaspis quercusmamma. They lay their eggs on the twigs of Bur Oak, and these little galls are formed around the eggs, a nice protective cover. The Cynipid wasps are minuscule, and these galls are very small too. Inside is a perfectly formed oval cocoon. The hole at the top shows that the gall is now empty.