Abstract:
The enigmatic Australo-Pacific genus Geochus Broun includes 26 described species from New Zealand and one from Lord Howe Island. They are abundant in leaf litter, and most species are easily recognized as adults by their odd squat form, lack of tarsal claws and flattened larvae that mine dead leaves. In older classifications, Geochus was placed in Curculioninae or Molytinae, but has been regarded more recently as an aberrant molytine or member of Phrynixini. A phylogeny of weevils that included Geochus from New Zealand and Lord Howe Island, representatives of 32% of the weevil genera in New Zealand, selected Rhamphini and Viticiini, and the South African genus Afrogeochus Rheinheimer, placed Geochus as the sister taxon of Viticis Lea, well outside Molytinae or Curculioninae at the base of a grade consisting of Entiminae, Cyclominae, and Phrynixini. Afrogeochus is transferred from Curculioninae to Cossoninae, based on molecular evidence. The absence of tarsal claws has hitherto been a distinct character of Geochus. However, their retention is reported in Geochus kuscheli Leschen, Davis, Brown, Brav-Cubitt, and Buckley, new species, a species that is sister to the remaining members of the genus. The status of type specimens for all 26 previously described Geochus species is reviewed, and eleven lectotype designations are made to promote a stable taxonomy for: Geochus apicalis Broun, Geochus convexus Broun, Geochus inaequalis (Broun), Geochus lateralis Broun, Geochus marginatus Broun, Geochus pictulus Broun, Geochus plagiatus Broun, Geochus politus (Broun), Geochus puncticollis Broun, Geochus rugulosus Broun, Geochus setiger Broun, Geochus similis Broun, Geochus squamosus Broun, Geochus suffusus Broun, Geochus tibialis Broun, and Geochus variegatus Broun. The 27 known Geochus species are grouped into 13 species groups, and a key to the adults of these species groups is provided.
