ABSTRACT. The previously unknown sexes of 13 species of Linyphiidae and Theridiidae are described and illustrated for the first time. These include the following members of the Linyphiidae: Centromerus furcatus (Emerton) female, Cheniseo sphagnicultor Bishop & Crosby female, Coloncus siou Chamberlin male, Dismodicus alticeps Chamberlin & Ivie female, Floricomus praedesignatus (Bishop & Crosby) female, Glyphesis idahoanus (Chamberlin) male, Gnathonaroides pedalis (Emerton) female, ...