Thanks. It's a good match with some of the images, but the ones from Utah are really different.

sometimes the pattern is faint, and it is variable too (within basic limits). What varies most though is the coloring. The colors tend to match the ground the insects live on, and the ones living on sand tend to be more "even" looking, often with fine speckling istead of bold spots. Most of the populations in Utah are found on sand. The ones on gravel, especially where the color of the gravel varies, tend to the most boldly marked (and perhaps prettiest).