Key to species of Luctithonus

1. Each elytron with longitudinal black macula on outer margin extending from humerus, along upper margin of epipleuron and onto disk toward suture, at the apical fourth or fifth; elytral pubescence without green tinge............. L. duartensis Lingafelter, new species

— Elytra without longitudinal black macula extending from humerus to apical fourth or fifth; elytral pubescence with at least partial green tinge...................................... 2

2. Elytra with abundant dark, well-defined elytral punctures throughout; narrow, white, transverse, crescent-shaped or ovoid pubescent macula near apex.......... L. pantherinus (Zayas)

— Elytra with dark, well-defined elytral punctures most prevalent at base and outer margin, sparse on disk and near suture; pubescent patch at apex, if present, not crescent-shaped or ovoid.......................................... L. aski Lingafelter, new species