Goldenrod round galls come in different sizes. Apparently the smaller ones get attacked by parasites more often than others; but the larger ones attract the hungry eye of chickadees in winter. So there are two opposite selective forces at work.
A goldenrod round gall has a rich fauna. In addition to several flies, some braconid wasps (subfamily Doryctinae) emerged from these galls, considerably smaller than the Eurosta flies, 2-3mm. Several females and one male, so far:
♀ ♂        A different one

I also found a mordellid beetle and larva


some Eulophids

and Eurytoma
E. gigantea larva E. gigantea ♀ E. gigantea ♂

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