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Maculated individuals are easily recognised. The dorsal surface is black usually with 4 or 6 orange spots (a few individuals may have 2 or no spots). Ventrally, all abdominal sternites have lateral orange spots. Immaculate individuals may be distinguished from the larger (usually) immaculate B. lyrata by the orange spots on all the sternites. Examination of the male genitalia is also diagnostic. Beetles range from 13 through 18.5 mm with a mean size of 15.4 mm (n=37). males tend to be slightly smaller than the females.

Details of the life cycle have not been worked out. Males of B. nuttalli come to the oviposition sites looking for females. On several occasions, male B. nuttalli have be observed in copula with the females of the wrong species, most commonly those of B. langi. No hybrid offspring have been found to date.

From Alaska in the north east to Quebec and south to Arizona and New Mexico. In Alberta specimens have been found in the boreal, foothills, and mountain conifer forests. No specimens have been collect to date in the Cypress Hills.