Black Widow Spiders UC Riverside Center for Invasive Species Research Center for Invasive Species Research http://cisr.ucr.edu/identifying_brown_widow_spiders.html Riverside research center website describes the differences http://cisr.ucr.edu/identifying_brown_widow_spiders.html cisr.ucr.edu Rick Vetter’s web page cisr.ucr.edu Identifying Brown Widow Spiders this UC Riverside website Rick Vetter’s web page Black Widow Spiders UC Riverside