Abstract

The Hawaiian spider genus Orsonwelles, gen. nov. (Araneae : Linyphiidae) is described. All Orsonwelles species are single island endemics: Kauai harbours six species; Oahu has three; Molokai has two; and Maui and Hawaii have one species each. The thirteen species included in Orsonwelles are described and illustrated: O. torosus (Simon), comb. nov., O. malus, sp. nov., O. calx, sp. nov., O. ventus, sp. nov., O. bellum, sp. nov. and O. iudicium, sp. nov. from Kauai; O. polites, sp. nov. (the type species), O. ambersonorum, sp. nov. and O. arcanus, sp. nov. from Oahu; O. othello, sp. nov. and O. macbeth, sp. nov. from Molokai; O. falstaffius, sp. nov. from Maui; and O. graphicus (Simon), comb. nov. from Hawaii. A total of 55 morphological characters (plus one behavioural character) were scored for twelve taxa (four Orsonwelles species plus eight linyphiid outgroups) to test the monophyly of the genus using cladistic methods. The most parsimonious cladograms provide robust character support for the monophyly of Orsonwelles. A single colonisation of the Hawaiian archipelago is hypothesised to explain the presence of these species in the Hawaiian Islands. This genus represents a case of insular gigantism (these are the largest linyphiids described), although the close relatives of Orsonwelles remain unknown. Their web architecture is also described and illustrated.