[3] Gall formation occurs on host leaf buds in the spring.

[4] Galls are apple-sized, up to 2" in diameter, with a bumpy, hairless, spotted texture.

[3] Internally, the larva resides in a central chamber with radiating white fibers called nutritive tissue which feed the larva with nutrients supplied by the host.

As the gall matures its external color changes from green to brown.

After the adult wasp emerges, the gall becomes brittle and "empty" when the nutritive fibers disintegrate.