It might be Sunflower Moth. They lay eggs on young coneflower flower buds and the hatched larvae tunnel around inside, leaving mounds of gritty frass (i.e. worm poop) on the surface.
They also attack many other members of the Daisy/Sunflower family. Where I grow my coneflowers, those nasty moths frequently ruin the whole stand. Chemical control may or may not work, but such chemicals are also very bad for the bees and other pollinators that love those coneflowers.
