The orb-weaving spider subfamily Arkyinae L. Koch, 1872 is exclusively found in the Australasian region and its taxonomy and the systematic relationships within and between genera of this subfamily are poorly understood. We here revise the arkyine genus Demadiana Strand, 1929 to include six Australian species, four of which are described as new: Demadiana simplex (Karsch, 1878) (type species), D. carrai, sp. nov., D. cerula (Simon, 1908), comb. nov., D. complicata, sp. nov., D. diabolus, sp. nov., and D. milledgei, sp. nov. A phylogenetic analysis based on an updated araneid morphological data matrix including 57 genera of orb-weaving spiders identified Demadiana as a member of the araneid subfamily Arkyinae. A separate phylogenetic analysis for the genus at the species level showed little resolution within Demadiana, but did identify a monophyletic Demadiana supported by three putative synapomorphies: small unique setal pits with spherical sockets covering the carapace, sternum and the bases of the paturon (chelicerae), an extreme elongation of the trumpet-like aggregate spigots of the posterior lateral spinnerets and a distinct curvature of the embolus. We detail several new generic and species synonymies within Arkyinae. Aerea Urquhart, 1891 (type species Aerea alticephala Urquhart, 1891) and Neoarchemorus Mascord, 1968 (type species N. speechleyi Mascord, 1968) are regarded as junior synonyms of Arkys Walckenaer, 1837 (type species A. lancearius Walckenaer, 1837), resulting in Arkys speechleyi (Mascord, 1968), comb. nov. Aerea magnifica Urquhart, 1893 and Archemorus simsoni Simon, 1893 are regarded as junior synonyms of Aerea alticephala Urquhart, 1891, and Arkys nitidiceps Simon, 1908 is proposed as a junior synonym of Arkys walckenaeri Simon, 1879.