1. Elytral sculpture different on basal and distal halves............................................................2

1′. Elytral sculpture uniform (or similar) throughout............................................................................ 3

2. Males: Last maxillary and labial palpomere notably enlarged at apex (longest width equal to about 0.65 times its length); cephalic carinae (Fig. 18) not notably elevated at apex. Females: Cephalic carinae slightly elevated (Fig. 23); antennae reaching about apex of basal 1/3 of elytra (sometimes almost elytral middle) (Fig. 23). Ecuador, Peru............................................................... Prionacalus atys

2′. Males: Last maxillary and labial palpomere slender towards apex (longest width 0.35– 0.45 times its length); cephalic carinae (Fig. 29) distinctly elevated at apex. Females: Cephalic carinae distinctly elevated (Fig. 37); antennae reaching base of distal 1/3–1/4 of elytra (Fig. 37). Ecuador, Colombia, Peru.......................................................... Prionacalus cacicus

3. Genal apex with long, acute projection (Fig. 42). Colombia.......... Prionacalus demelti

3′. Genal apex with short, acute projection or rounded and not projected (Figs. 53, 66, 78).......................................................................4

4. Prosternal process with spiniform projection on underside of apex (Fig. 14); protibia of male enlarged near middle. Ecuador.................................................. Prionacalus whymperi

4′. Prosternal process without spiniform projection on underside of apex or with rounded projection (Fig. 15); protibiae of male gradually enlarged from base................................5

5. Cephalic carinae almost indistinct in both sexes (Figs. 66, 72); sulcus between cephalic carinae distinctly deep (Fig. 66). Argentina, Bolivia, Peru....... Prionacalus woytkowskii

5′. Cephalic carinae distinct, mainly in males (Figs. 78, 84, 124); sulcus between cephalic carinae slightly or moderately deep (Figs. 78, 84, 124).........................................................6

6. Antennae of male not reaching elytral apex (Fig. 124). Female unknown. Peru..................................................... Prionacalus uniformis

6′. Antennae reaching or surpassing elytral apex in male (Fig. 76), and distal 1/ 3 in female (Fig. 84). Ecuador, Peru....... Prionacalus iphis