Diagnosis.--Key characters: Ommatidial size coarse (Fig. 39b); prosternal process not planar and with apex slightly expanded (Fig. 18); mesal antennal spines present (Figs. 8b, 9b); pronotum with impunctate regions present; femoral carinae absent; procoxal cavities open laterally (Fig. 17); lateral projections into mesocoxae from mesosternum absent (Fig. 20); femoral apices rounded; dense golden or silver pubescence absent from elytra; tibial carinae present (Fig. 22); profemoral shape clavate (Fig. 37b); elytral sutural spines absent or very weak (Fig. 15e); lateral antennal spines absent; antennomeres linear, not expanded apically; elytra with apicolateral spine shifted to apicomedial position; elytra and pronotum with dense vestiture of short pubescence; lateral pronotal tubercles present and acute on most specimens (Fig. 12f); elytra without dark outlining of perimeter as viewed from above. Length: 9-26 mm.
Distribution and Diversity.--Panamá, Peru, French Guyana, Brazil, Bolivia. Sixteen species.
Discussion.--The movement of the apicolateral spine to an apicomedial position is a synapomorphy showing the relationship of Mephritus to Sphaerion and Miopteryx (Fig. 60).
Mephritus runs near Miopteryx in the key but differs in having (in most specimens) lateral pronotal tubercles present and acute (Fig. 12f) (absent in Miopteryx). Mephritus species do not have the elytra with a darkened perimeter as in Miopteryx. Mephritus differs from Sphaerion in having procoxal cavities open laterally (closed in Sphaerion), but otherwise they greatly resemble each other.