A new species of Compsodactylus Fuhrmann, 2012 (Coleoptera: Scarabaeidae: Melolonthinae: Macrodactylini) is described from Peru. New provincial records for Compsodactylus argentinus (Moser, 1919) are detailed for Argentina: Córdoba and Misiones. A revised key to Compsodactylus species is presented.

Key words: Macrodactylini, Argentina, Peru, Neotropics, taxonomy

Compsodactylus mendax Fuhrmann & Smith, new species

Diagnosis. Length greater than 8.0 mm; dorsal surface with metallic green reflections; antennae with 10 antennomers; clypeus elongate with expanded apex in males (Fig. 4); clypeus with short, spiny setae along apex and lateral edges in males; apex of protarsomere I 2 times wider than apex of protarsomere II in males; elytral striae distinctly punctate; male metatibial apex with an inner truncate, twisted process (Fig. 16); genitalia of females with gonostyle, and gonocoxite about 2.5 times longer than wide (Figs. 23−25).

Etymology. From the Latin mendax meaning liar, in reference to the elongate clypeus being reminiscent of Pinocchio’s nose. This name is a noun in apposition.