Key to species of Columbianum from Amazonia

Note that it would be preferable for the key to include all species of Columbianum, but as some of the published descriptions are poor this would require more comprehensive work which is outside the scope of this study.

1 Large, dark and robust species, body width at least 1.8 mm ................................... C. major sp. nov. – Smaller species, body width less than 1.0 mm ................................................................................. 2

2 With strongly domed head and very narrow rostrum; head and metazonites with tubercles but not appearing rugose; prozonites wider than metazonites; medium sized (body width 0.8–1.2 mm) ...... ........................................................................................................................................ C. nahvalr sp. nov.

– With clear distinction between head and rostrum, but head not strongly domed; very rugose, with abundant tubercles on head and metazonite; prozonites the same width as metazonites or narrower; smaller size (body with 0.59–0.98 mm) .................................................................... C. adisi sp. nov.

See also Table 1 for comparisons between the three species.