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Even if you can estimate a circle of possible host plants (Cirsium and Centaurea species) growing there, it can clarify the situation. Many local populations of Urophora spp. shift from one host to another. But the most probable candidates look to be large Cirsium spp., e.g., Cirs. eriophorum (the host of U. terebrans) or another, previously unknown to be a host of U. congrua.
But, again: montane populations often look darker than the lowland ones...