Key to species-groups of Protopolybia Ducke

1. Species with posterior aspect of propodeum gently convex around a narrow median groove or with posterior face projecting symmetrically to either side of median groove, forming two moderately high protuberances (Fig. 23)..................................................................................................... P. exigua species-group.

– Species with posterior aspect of propodeum with a wide and shallow cavity (Fig. 24 and 25)...........................2

2. Occipital carina strong and salient throughout (Fig. 26 and 27) and pronotal pretegular carina, posteriorly adjacent area strongly developed, adjacent area wider and T 1 in dorsal view with petiole very short; distal margin wider and nearly straight, cup-like (Fig. 30 and 31)........................................................... P. picteti-emortualis species-group.

– Occipital carina fading at some point near the middle of gena height or fading very close to the insertion of the mandible (Fig. 28 and 29); T 1 in dorsal view with petiole and distal margin variable (Fig. 32 and 33)............................... 3

3. Large and robust species, with length of fore wing between ca. 5.1–5.7mm. T2 with shape of tergum wider than long, profile strongly bulging antero-laterally, spiracles tending to face forward (Fig. 34 and 35). Color black with yellow marks (Fig. 1-10)............................................................................ P. chartergoides species-group.

– Small and slender species, with length of fore wing between ca. 4.75–5.1mm. T2 with shape of tergum wider than long, anterior contour distinctly convex in both dorsal and lateral view (Fig. 36 and 37), spiracles not tending to face foreward. Color variable, brown or entirely yellow with few black marks........................................... P. sedula species-group.