An insect called the Acorn Weevil lays eggs inside ripe acorns where the wormy offspring consume their nutty meals in safety. Uneaten worms eventually exit as beetles from a hollow acorn. When the young beetles exit, the empty acorn shell is a waiting apartment for spiders, millipedes, or the eggs of the Acorn Moth. Eventually the acorn is decomposed by fungi and reverts to soil. The bark fissures of a mature oak tree often hide tiny insects, spiders, insect larvae, and the stored seed-meals of nuthatches and woodpeckers.
Young spiders use the catkin-like oak flowers as niches, where they trap small insect meals.
Warblers and other insect-eating birds glean the tender leaves for camouflaged caterpillars and the grown spiders. Native leaf-eating insects rarely kill off the oak trees. The phenols stunt caterpillar growth and reproduction. Predatory insects such as assassin bugs, caterpillar hunters and mantises prey on the leaf-eating worms, too. Blankets of oak leaves collect on the ground each fall.