1 Metasternal process marginate anteriorly; antennomeres 1–3 entirely pale yellow in most specimens or antennomeres 2 and 3 slightly infuscate dorsally in a few specimens [eastern: New Brunswick to South Dakota, south to Texas and northeastern Georgia] ............................................................................................. B. variegatum Say
– Metasternal process not marginate anteriorly; antennomeres 1–3 or at least 2 and 3 clearly infuscate on dorsal side..................................................................................... 2
2 Pronotum markedly constricted at base (WP/WP b = 1.33–1.39; n = 10), side markedly widely rounded [eastern: Nova Scotia to Minnesota and South Dakota, south to Iowa, Illinois, West Virginia and Virginia] ....................................... B. graciliforme Hayward
– Pronotum less constricted at base (WP/WP b = 1.13–1.29; n = 50), side less widely rounded.......................................................................................................................... 3
3 Pronotum entirely or largely reddishbrown or brown, clearly not as dark as head dorsally; femur entirely pale; submedian pale marking of elytral interval 5 quite distinctly set off from markings on adjacent intervals [eastern: Newfoundland to the New England states, west to Iowa] .................................................... B. immaturum Lindroth
– Pronotum entirely or largely reddishblack to black, as dark as head dorsally; femur infuscate, at least around middle, in the vast majority of specimens; submedian pale marking of elytral interval 5 not clearly set off from markings on adjacent intervals.. 4
4 Pronotum more constricted at base (WP/WP b = 1.24 [1.21–1.29]; n = 20); basal edge truncate to slightly oblique toward posterior angle; lateral depression better defined in most specimens, without or with poorly impressed microsculpture meshes; microsculpture on head and lateral margins of pronotum with sculpticells flat; submedian dark marking on elytral interval 2 quite distinctly extended anteriorly to near scutellum; dark marking on elytral interval 4 reaching basal fourth of elytra [transcontinental: Newfoundland to Alaska, south to the Sierra Nevada in northeastern California, Colorado, North Dakota, Michigan, and Pennsylvania; also eastern Siberia]........................ ................................................................................................... B. incrematum LeConte
– Pronotum less constricted at base (WP/WP b = 1.15 [1.13–1.18]; n = 20); basal edge moderately oblique toward posterior angle; lateral depression less defined, with microsculpture meshes more distinct; microsculpture on head and lateral margins of pronotum with sculpticells convex; submedian dark marking on elytral interval 2 not or not quite distinctly extended anteriorly; dark marking on elytral interval 4 not reaching basal fourth of elytra or widely interrupted behind level of anterior discal seta ................................................................. B. iridipenne Bousquet and Webster, sp. nov.