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ID is difficult, indeed. There is an article by White and Marquardt (1989), with a key, which has not been updated since then. Reddish vittae on mesonotum and 4 pairs of black dots are in C. jaceae and C. acrolophi, but the latter, as well as C, australis is generally smaller and has more pependicular 2nd and 3rd crossbands (oblique in C. jaceae).
More precise ID requires females, dissections and measurements, or exact association with host plant (C. jacea). So this is certainly C. jaceae.