Key to the species of Procestus

1. Frons with a median horn and a lateral tubercle. Epomia connected across top of pronotum with epomia on opposite side. Posterior transverse carina of propodeum complete (Fig. 15). Mexico .............................. P. nabis Townes, 1970

- Frons simple (unarmed) (Figs 2, 3 & 5). Epomia not connected across top of pronotum with epomia on opposite site. Posterior transverse carina of propodeum absent (Figs 9, 10 & 21)...................................................... 2

2. Metasoma black................................................................... P. simplex Townes, 1970

- Metasoma mostly yellow............................................................................... 3

3. Metapleuron mostly black. Apical part of metasoma mostly black. Apical part of fore wing with a brownish spot. Costa Rica ......................................................................... P. pammae Ugalde & Gauld, 2002

- Metapleuron mostly yellow. Apical part of metasoma mostly brownish. Apical part of fore wing with a blackish spot. Brazil ....................................................... Procestus jatai sp. n. Herrera-Flórez & Penteado-Dias