Reddish copper colouration, much overlain by dense white mealiness, especially on the ventral side. Pronotum mostly with coarse puncturation, but a zone of denser and finer puncta medially in the anterior. Compared to M. scintillans, the lateral margins of the pronotum are more strongly contracted towards the anterior and posterior (but less so than in M. globithorax), and the elytra are more strongly tapered apically, and have much smaller puncta and more clearly defined costae which are scarcely punctate. Distinguished from M. globithorax by the elytra having tridentate apices and intercostal areas which are densely and finely punctate and much wider than the costae (ribs).
Differs from Notobubastes costatus in the broader body shape, more rounded pronotum with a longer and more pronounced median sulcus, and areas of coarser puncta and sculpturing on the pronotum and elytra.

The live specimen of this taxon illustrated above was collected from NW of Port Augusta by Mark A. Hura in December 2008. It is treated here as an undescribed species of Microcastalia, although it might as easily fit Notobubastes a genus considered by Bellamy & Peterson 2000 to be closely related and 'perhaps the sister group' to Microcastalia. Their maintenance as two separate genera warrants investigation. Microcastalia is the older name and would have priority.

The specimen was included in M. scintillans by (Lang & Stolarski 2020), and treated similarly on this website until June 2023. According to Mark (T.M.S.) Hanlon, the same taxon is known to occur in WA.

This species has the same white powdery excrescence in the puncta and other declivities as found on M. globithorax when fresh.

The SA specimen was found sitting on a branch of a young Western Myall (Acacia papyrocarpa), and its pristine condition raised the possibility that it might have only recently emerged from its host. However, in WA it is known to be associated with stems and branchlets of Hop-bush (Dodonaea) species (M. Powell; M.Hanlon, pers. comm. 2020).