Much like Procecidochares atra galls on goldenrods, but much smaller and more cryptic. The swollen bud is usually axial, and often obscured from above by the tiny overtopping leaf blades of the constituent modified leaves. The larva has several black, elliptical splotches along one side. Occurs more often among the flowering branches. Host range includes this Symphyotrichum species in Quebec, from galls discovered by Christian Grenier, which I am unable to identify.