1 Prothoracic hypomera with deep antennal cavities that are clearly limited posteriorly, and completely contains the antennae while in repose (Figs. 39, 41); elytra usually with at least partially visible velvety arcuate patches; elytra with elevated sculpture reduced, at most to single weak median nodule at start of apical declivity. California Floristic Province. Figs. 35–36 ............................................................................................................... P. diabolicus (LeConte)

- Prothoracic hypomera with deep antennal cavities that are incomplete and not limited posteriorly (Fig. 40), or broad shallow depression (Fig. 42); elytral vestiture variable; elytra with three distinct nodules at start of declivity, two offset medially, and one laterally....................................................................................................................................... 2

2 Prothoracic hypomera with deep antennal cavity that is not limited posteriorly (Fig. 40); elytral vestiture uniform in coloration from dark red to black; with only three nodules in area of declivity; length rarely over 20mm. California Floristic Province. Fig. 37 ............................................................................................................. P. plicatus (LeConte)

- Prothoracic hypomera with shallow depression, lacking distinct cavity (Fig. 42); elytral vestiture mottled whitish to black, with velvety spots along suture and on ridges; with three nodules in declivity area and fourth nodule near apex of elytra; length usually over 20mm. Central America. Fig. 38 ............................................... P. venustus (Champion)