Banasa tumidifrons Thomas and Yonke is a little-known stink bug of the nominotypical tribe of the subfamily Pentatominae. Described from California, Idaho, and Oregon, it since has been recorded only from Washington State. Adults are known from juniper (Juniperus), but it is not known whether junipers support the pentatomid's nymphal development. From 2012 to 2014, nymphs and adults were collected from Rocky Mountain juniper (J. scopulorum) in natural communities and ornamental plantings at 18 sites in five states: Colorado, Kansas, Nebraska, South Dakota, and Wyoming; all are new state records. Nymphs of all instars (I–V) were found on female plants of the dioecious J. scopulorum in early July and instars II–V in early to mid-September. Juniperus scopulorum is considered a host plant in a restricted sense of the term: a plant on which nymphs feed and develop. Occasionally present on junipers were fifth instars of three other pentatomids: B. euchlora Stål (Wyoming is a new state record), Thyanta calceata (Say), and T. custator accerra McAtee.