Key to the known species of Ptenidium (Peruvium) from Peru

1. Pronotum and elytra with long pubescence.......................................................... capillatum

- Head only with long pubescence.......................................................................... 2

2. Large species> 1.2mm ............................................................................. grande

- Smaller species <1.0 mm............................................................................... 3

3. Antennae short, (Fig. 37)...................................................................... brevissimum

- Antennae longer (Figs. 38,39)............................................................................ 4

4. Scutellum with a central carina (Fig. 23)............................................................ carinatum

- Scutellum with at most a small carina in the centre of the anterior margin......................................... 5

5. Pronotal hind angles without clearly protruding setae, males with a short line of setae in the centre of the metaventral posterior margin (Figs. 45–47)........................................................................... inornatum

- Pronotal hind angles with clearly protruding setae............................................................6

6. Narrow, more parallel sided species, lateral margins of pronotum less rounded (Fig. 4)....................... contractum

- Lateral margins of pronotum more rounded, male with tuberosities on head (Fig. 8)........................... gibbosum