By rough count, I have 77 wasp, midge, mite, and aphid gall-inducers logged on iNaturalist, most of them in Brooklyn, and most of these in Green-Wood Cemetery.
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This work by Matthew Wills is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Backyard and Beyond 
So, where are the swarms of ladybeetles and other such predators that should be feeding on these galls?
The galls themselves are plant material which serve to both shelter and feed the inducer larvae within. Not a lot of things eat the actual galls. I’ve seen holes on woodsy bullet galls that suggest woodpeckers have been at work. The lifeforms within is juicy, of course, but it’s relatively protected. There are some parasitic wasps who lay their eggs inside the galls, the resulting larva eating the original gall-inducer larva.
To quote my brother, “everybody is on somebody’s menu at dome time”. I expected there to be a long list of predators and parasites taking advantage of this food source. Go figure.