Carduus nutans (Musk or Nodding Thistle)
Fortunately, this thistle is an annual and can be managed more easily than Canada thistle. The biological control imported to control this plant has been found in native thistles as well.
Euphoria inda, or Flower Bumble Beetle, is frequently found in Musk Thistle flowers. It does not limit itself to thistles, however, as I found one in a Ragweed pant recently. They are aptly named, and also the cutest of beetles.
Euphoria embedded in a thistle flower.