Spiders from Riversidian coastal sage scrub with comparisons to Diegan scrub fauna (Arachnida : Araneae)

We provide a list of 166 spider species collected from Riversidian coastal sage scrub (CSS) located within the Southwestern Riverside County Multispec ies Reserve in southern California. Spiders were collected over a two-year period from pitfall traps, vacuum samples, and malaise traps; additional sp ecies were collected by hand or in yellow pan traps. One hundred and twenty -seven species, representing 30 araneomorph families and one mygalomorph fa mily, were separated from the combined pitfall, vacuum, and malaise samples from 24 undisturbed Riversidian CSS plots. Three species occurred only in malaise samples, 58 species occurred only in pitfall samples, and 37 specie s occurred only in vacuum samples. An additional 39 species were collected by hand or in yellow pan traps (two species), among which were representati ves of two mygalomorph families not represented in pitfall catches. Over 33 % of the Riversidian species were unrecorded from our recent Diegan CSS stu dy bringing the combined total to 255 species. Eighteen species are new rec ords for Riverside County. At least eleven species are believed to be undes cribed. Six non-native species. Holocnemus pluchei (Scopoli). Dysdera croca ta C. L. Koch. Zelotes nilicola O. P.-Cambridge, Oecobius annulipes Lucas. Steatoda triangulosn (Walckenaer). and Menemerus bivittatus (Dufour). were among the species collected. Phenology data are provided for the 12 most pr evalent species. Natural history data are provided for habitat preference o f several species and on ant predation by three species. Non-native and end emic spider taxa are discussed. Comparison of Riversidian fauna to Diegan f auna suggested higher species diversity in Diegan CSS.