Based on Kerremans 1898, D. semiobscura differs from D. modesta in having the elytra purple (vs. purplish black) with light grey speckles (vs. traces of grey mottling), the antennae & tarsi 'obscure' [= dark] (vs. black), and the pronotum and scutellar region purple (vs. a shiny copper purple). Also the head is purple (vs. green), but this may simply be a result of different sexes being described. Structural differences apparent in the accounts of the two species seem slight and inconsequential: dimensions 5 x 1.8 mm (vs. 5 x 1.7 mm); pronotum sides fairly arched (vs. arched); pronotum base with median lobe barely indented (vs. a little indented); elytra with rugosities resembling scales (vs. with small transverse wrinkles).
This taxon is closely related to, and difficult to distinguish from, Diphucrania modesta (q.v.) which has an identical aedeagus; it may not warrant recognition as a distinct species. Its original description (as Cisseis semiobscura) by Kerremans 1898 was preceded on the same page by an adjacent protologue for C. modesta. Kerrremans introduced C. semiobscura stating that it had the appearance of C. modesta but was different in regard to certain details of structure and colouration, but did not elaborate further. The differences given under 'Distinctive features' above are derived from a comparison of his brief descriptions for the two species.
Analysis of preliminary DNA barcode sequences (mitochondrial CO-1) divided D. modesta and D. semiobscura samples into two tightly clustered and well separated sister groups: a sample of six individuals from the Mt Lofty Ranges (Belair, Mt Barker, Lobethal and Kapunda areas) and a sample of nine individuals from the Murray Mallee, southern Flinders Ranges and Eyre Peninsula (Monarto, Quorn, Kimba and Edilillie areas). The first group includes some 'typical' D. modesta forms with blackish elytra and coppery pronotum, and the latter some with more purplish elytra and pronotum that fit C. semiobscura. However, forms from the southern Mt Lofty Ranges (including some samples that grouped with typical C. modesta) often have the elytra dark coppery bronze to purplish rather than blackish. There is much variation, and it is not possible to find consistent colour or morphological differences corresponding to the two groups, nor any distinction based on adult host plants. A more detailed study with nuclear DNA may help resolve the taxonomy of this complex.
¹ Legend | regions | SA State Herbarium regions (map)
EA: Eastern, EP: Eyre Peninsula, FR: Flinders Ranges, GT: Gairdner-Torrens, KI: Kangaroo Island, LE: Lake Eyre, MU: Murray, NL: Northern Lofty, NU: Nullarbor, NW: North-Western, SE: South-Eastern, SL: Southern Lofty, YP: Yorke Peninsula |
| size | The ellipse is the correct size when printed, indicative on a desktop screen, and likely to be wrong on a mobile device. |