Males bright metallic green to golden green (or coppery, especially in some Flinders Ranges specimens); females more subdued blue-grey green to grey-bronze, sometimes with purplish tints; mostly lacking hairs dorsally and ventrally; generally with a dense and even distribution of small punctures. Elytra without distinct costae.

This species was described by Germar 1848 (as Buprestis simplex) based on a type collection from Adelaide. It is still common on foliage of Golden Wattle Acacia pycnantha in the Adelaide area. This is a leaf-eating species found on that host plus a few other Acacia species in the more temperate areas of the Mt Lofty Ranges through to the central Flinders Ranges. Records from EP and MU Regions are confined to the western margin of the southern Flinders Ranges and the eastern margin of the Mt Lofty Ranges respectively.

Melobasis simplex often occurs together with a similarly proportioned bronze-coloured species, M. sordida, which Carter 1929 had placed in synonymy under it. Melobasis sordida, however, is clearly a distinct species and was assigned to a different species group by Levey 2018.

As defined here M. simplex also excludes M. semisuturalis Blackburn, 1887 which is a member of the M. purpurascens species group.

Adults are found mostly on the foliage of a number of Acacia species and only rarely on other genera. I have reared adults from billets cut from the dead stems of two common adult host species: Golden Wattle (Acacia pycnantha), and Wirilda (A. retinodes).